Temperature-Dependent Kinetics of the Reactions of the Criegee Intermediate CH2OO with Aliphatic Aldehydes.

Criegee intermediates, formed by alkene ozonolysis in the troposphere, can react with volatile organic compounds (VOCs). The temperature-dependent kinetics of the reactions between the Criegee intermediate CH2OO and three aliphatic aldehydes, RCHO where R = H, CH3, and C2H5 (formaldehyde, acetaldehyde, and propionaldehyde, respectively), have been studied using a laser flash-photolysis transient absorption spectroscopy technique. The experimental measurements are supported by ab initio calculations at various composite levels of theory that characterize stationary points on the reaction potential and free energy surfaces. As with other reactions of CH2OO with organic carbonyls, the mechanisms involve 1,3-dipolar cycloaddition at the C=O group, over submerged barriers, leading to the formation of 1,2,4-trioxolane secondary ozonides. The bimolecular rate constants of all three reactions decrease with increasing temperature over the range 275-335 K and are characterized by equations of Arrhenius form: k(T) = (7.1 ± 1.5) × 10-14exp((1160 ± 60)/T), (8.9 ± 1.7) × 10-15exp((1530 ± 60)/T), and (5.3 ± 1.3) × 10-14exp((1210 ± 70)/T) cm3 s-1 for HCHO, CH3CHO, and C2H5CHO, respectively. Based on estimated concentrations of CH2OO, the reactions with aldehydes are unlikely to play a significant role in the atmosphere.

Temperature-Dependent Kinetics of the Reactions of the Criegee Intermediate CH2OO with Hydroxyketones.

Though there is a growing body of literature on the kinetics of CIs with simple carbonyls, CI reactions with functionalized carbonyls such as hydroxyketones remain unexplored. In this work, the temperature-dependent kinetics of the reactions of CH2OO with two hydroxyketones, hydroxyacetone (AcOH) and 4-hydroxy-2-butanone (4H2B), have been studied using a laser flash photolysis transient absorption spectroscopy technique and complementary quantum chemistry calculations. Bimolecular rate constants were determined from CH2OO loss rates observed under pseudo-first-order conditions across the temperature range 275-335 K. Arrhenius plots were linear and yielded T-dependent bimolecular rate constants: kAcOH(T) = (4.3 ± 1.7) × 10-15 exp[(1630 ± 120)/T] and k4H2B(T) = (3.5 ± 2.6) × 10-15 exp[(1700 ± 200)/T]. Both reactions show negative temperature dependences and overall very similar rate constants. Stationary points on the reaction energy surfaces were characterized using the composite CBS-QB3 method. Transition states were identified for both 1,3-dipolar cycloaddition reactions across the carbonyl and 1,2-insertion/addition at the hydroxyl group. The free-energy barriers for the latter reaction pathways are higher by ∼4-5 kcal mol-1, and their contributions are presumed to be negligible for both AcOH and 4H2B. The cycloaddition reactions are highly exothermic and form cyclic secondary ozonides that are the typical primary products of Criegee intermediate reactions with carbonyl compounds. The reactivity of the hydroxyketones toward CH2OO appears to be similar to that of acetaldehyde, which can be rationalized by consideration of the energies of the frontier molecular orbitals involved in the cycloaddition. The CH2OO + hydroxyketone reactions are likely too slow to be of significance in the atmosphere, except at very low temperatures.

Living with Parkinson's in England during and beyond COVID-19 restrictions: a longitudinal qualitative study.

OBJECTIVES: Government-enforced lockdown restrictions associated with preventing the spread of the COVID-19 virus had a series of unintended, negative effects. One group of individuals whose physical and mental health was significantly and disproportionately impacted were those with Parkinson's. However, research has been mainly cross-sectional, with no previous study qualitatively following up participants through both lockdowns and the easing of restrictions. Consequently, this study aimed to provide a detailed understanding of the experience of lockdowns and the easing of restrictions on the physical and mental health of people with Parkinson's. METHOD: Data from semi-structured interviews collected at four time points across an 18-month period (May 2020 - September 2021) from the same participants (six men and four women) were analysed using interpretative phenomenological analysis. RESULTS: Three themes were derived: (1) Wrestling with a Parkinson's identity, agency and control during the pandemic; (2) The encroachment and acceleration of a Parkinson's future; and (3) Recalibrating priorities from COVID-19 to Parkinson's. CONCLUSION: As currently the only published study to provide an in-depth longitudinal analysis with this population, we used a more dynamic theoretical account, Strauss and Corbin's theory of illness trajectories, to understand the findings and suggest ways of supporting individuals with Parkinson's in this stage of the pandemic. The scale and breadth of the support needed is a significant challenge for current statutory systems.

Midwives' perspectives and perceptions in relation to perinatal psychotic-like experiences: a qualitative study.

BACKGROUND: Psychotic-like experiences (PLEs) refer to subclinical experiences consistent with psychosis that may include hearing, feeling or seeing things that others cannot, or experiencing unusual beliefs. These experiences appear to be more common during the perinatal period. There appear to be barriers which make it difficult for midwives to support mothers with mental health difficulties. However, it is important that midwives can provide support with PLEs. AIM: This study aimed to explore UK midwives' perspectives and perceptions relating to mothers' psychotic-like experiences in the perinatal period. METHODS: A qualitative study using semi-structured interviews with ten midwives recruited online was conducted. Transcripts were analysed using thematic analysis. RESULTS: Four themes were developed: (1) Identifying psychotic-like experiences would be complicated; (2) Psychotic-like experiences can feel overwhelming for women and midwives; (3) This is my responsibility: I'll do what I can to support women even if it's hard; and (4) The system feels unsafe and insecure which makes the anticipated role in supporting psychotic-like experiences harder. CONCLUSION: Midwives described their motivation to support mothers with PLEs but articulated many factors that made this difficult. The results emphasise the importance of training and guidance for midwives to support them being able to offer support and information to mothers. The findings also highlight the importance of systemic safety for midwives alongside support through supervision and reflective practice.

Acetylacetone Photolysis at 280 nm Studied by Velocity-Map Ion Imaging.

The photolysis of acetylacetone (AcAc) has been studied using velocity-map ion imaging with pulsed nanosecond lasers. The enolone tautomer of AcAc (CH3C(O)CH═C(OH)CH3) was excited in the strong UV absorption band by UV pulses at 280 nm, preparing the S2(ππ*) state, and products were probed after a short time delay by single-photon VUV ionization at 118.2 nm. Two-color UV + VUV time-of-flight mass spectra show enhancement of fragments at m/z = 15, 42, 43, 58, and 85 at the lowest UV pulse energies and depletion of the parent ion at m/z = 100. Ion images of the five major fragments are all isotropic, indicating dissociation lifetimes that are long on the timescale of molecular rotation but shorter than the laser pulse duration (<6 ns). The m/z = 15 and 85 fragments have identical momentum distributions with moderate translational energy release, suggesting that they are formed as a neutral product pair and likely via a Norrish type I dissociation of the enolone to form CH3 + C(O)CH═C(OH)CH3 over a barrier on a triplet surface. The m/z = 43 fragment may be tentatively assigned to the alternative Norrish type I pathway that produces CH3CO + CH2C(O)CH3 on S0 following phototautomerization to the diketone, although alternative mechanisms involving dissociative ionization of a larger primary photoproduct cannot be conclusively ruled out. The m/z = 42 and 58 fragments are not momentum-matched and consequently are not formed as a neutral pair via a unimolecular dissociation pathway on S0. They also likely originate from the dissociative ionization of primary photofragments. RRKM calculations suggest that unimolecular dissociation pathways that lead to molecular products on S0 are generally slow, implying an upper-limit lifetime of <46 ns after excitation at 280 nm. Time-dependent measurements suggest that the observed photofragments likely do not arise from dissociative ionization of energized AcAc S0*.

Fathers' Relational Experiences of Stillbirth: Pre-natal Attachment, Loss and Continuing Bonds Through Use of Objects.

This study aimed to investigate fathers' lived experiences of stillbirth through the lens of continuing bonds and use of objects. Semi-structured interviews were conducted with six fathers who had experienced stillbirth from 20 weeks gestation. Interpretative phenomenological analysis revealed five themes: loss and continued bonds in a mother-mediated dynamic, objects as manifestations of relational and meaningful memories, exerting existence and continued connection to others, continued bond through physical presence and evolving expressions of love and fatherhood. Findings offer a novel understanding of the relationship between objects and continued bonds, where objects are seen to facilitate this bond through varying means, including physical manifestation of the deceased and representation of the father-infant relationship. The study places importance on fathers' involvement in creating objects permeated with meaning and memories, and of validating fathers' experiences of loss rather than considering these men merely as partners of a mother who lost their own baby.

The Use of the Saccadometer to Identify Saccadic Characteristics in Myasthenia Gravis: A Pilot Study.

BACKGROUND: Myasthenia gravis (MG) often presents with ocular signs that mimic other forms of ocular defects, such as isolated cranial nerve palsy. Normal velocity or even hyperfast saccadic eye movements in the presence of deficits of smooth pursuit have been well described in the literature in myasthenic patients. The reason for these paradoxical clinical findings has been reported to be due to increased postsynaptic folding of the fast-twitch fibers responsible for the execution of a saccade which is absent in those fibers responsible for slower, smooth eye movement. Saccadic characteristics therefore offer a point of differential diagnosis between patients suspected of having ocular motility deficits as a result of MG and those caused by other neuropathies. The advent of portable quantitative saccadic assessment means that previously laboratory-based assessments that require specialist equipment and training may now be undertaken clinically, providing a noninvasive test that can aid the differential diagnosis of the condition. The aim of this pilot study was to investigate the feasibility of the saccadometer (Ober Consulting, Poznan, Poland) in detecting the saccadic characteristics associated with myasthenia, specifically normal peak velocity (PV) in a group of patients confirmed with myasthenia. METHODS: A group of 5 patients with a confirmed diagnosis of MG were recruited from a single site into the study along with 5 age-matched healthy volunteers. All myasthenic patients had ocular signs such as underaction or limitations of motility confirmed through ocular clinical examination. Healthy volunteers were screened for any underlying ocular motility or neurological defects before inclusion within the study. All participants undertook 100 trials of both 10 and 20° amplitude saccades, and mean PV, amplitude, and latency were recorded using the saccadometer for each individual. Overall, mean PV, amplitude, and latency were collated for both myasthenic and healthy control groups for each saccade size and compared. RESULTS: The mean PV was significantly greater (481 ± 103.5 deg/seconds) for myasthenic patients compared with healthy controls (384 ± 42.8 deg/seconds) (P < 0.05) in 10° saccades. PV was also greater in myasthenics for 20° saccades; however, this difference did not reach statistical significance for patients with MG (547 ± 89.8 deg/seconds vs 477 ± 104.5 deg/seconds) (P = 0.14). The latency of participants with MG was not significantly different from those of age-matched healthy participants in 10° saccades but was significantly different for 20° saccades. There was no difference in amplitude measured between the groups. CONCLUSIONS: PV for both 10 and 20° saccades was greater in myasthenic patients compared with healthy controls. All myasthenic patients produced normal velocity saccades in the presence of deficits of smooth ocular motility. The results from this small pilot study demonstrate the potential use of the saccadometer in a clinical setting to provide a noninvasive aid in the diagnosis of patients suspected with myasthenia.

The Nine Cancer Frames: A Tool to Facilitate Critical Reading of Cancer-Related Information.

People's ability to critically assess cancer-related information is essential from a preventional and therapeutic, as well as a general democratic perspective. Such cancer literacy is not just about acquiring factual knowledge. It also involves the ability to analyze how the information is contextualized-how cancer is framed. Previous research concerning the framing of cancer in public discourse is voluminous and penetrating but also fragmented and inaccessible to non-experts. In this study, we have developed an integrated and applicable tool for analyzing cancer discourse by systematically classifying distinctive ways of framing of the concept of cancer. Building on previous research and an inductive framing analysis of a broad range of public cancer discourse, systematically selected from British and Norwegian newspapers, we have characterized nine cancer frames: the biomedical, the environmental, the epidemiological, the personal, the sociopolitical, the economic, the antagonistic, the alternative, and the symbolic frame. This framing scheme may be applied to analyze cancer-related discourse across a plurality of themes and contexts. We also show how different frames combine to produce more complex messages, thereby revealing underlying patterns, strategies, and conflicts in cancer communication. In conclusion, this analytical tool enables critical reading of cancer-related information and may be especially useful in educational initiatives to advance health communication and public understanding of cancer.

Becoming a mother in the context of sex work: Women's experiences of bonding with their children.

Many females engaged in sex work are mothers, often experiencing poverty, violence, marginalization, and psychological distress, factors also found to affect parental bonds. However, little is known about how this context impacts the bonding process. Given the ubiquity of sex work across geographical territories, understanding the relationship it has with mother-child bonding is an important international consideration in providing healthcare for sex working mothers and their children. Therefore, in this study we sought to explore women's experiences of bonding with their children in the context of sex work. We interviewed six women in the UK who were sex working during the first two years of their child's life about their bonding experiences and analyzed transcripts using Interpretative Phenomenological Analysis. We identified four themes were identified: (1) the complex process of bonding; (2) the role of powerlessness on bonding; (3) the powerful impact of receiving help, and (4) new perspectives of the body and sex work following motherhood. Findings contribute to the research literature on bonding by emphasizing the value of supportive care and the importance of social context, indicating specific factors to inform psychological support among sex working women.

Kinetics of the Reactions of CH2OO with Acetone, α-Diketones, and ß-Diketones.

Rate constants for the reactions between the simplest Criegee intermediate, CH2OO, with acetone, the α-diketones biacetyl and acetylpropionyl, and the ß-diketones acetylacetone and 3,3-dimethyl-2,4-pentanedione have been measured at 295 K. CH2OO was produced photochemically in a flow reactor by 355 nm laser flash photolysis of diiodomethane in the presence of excess oxygen. Time-dependent concentrations were measured using broadband transient absorption spectroscopy, and the reaction kinetics was characterized under pseudo-first-order conditions. The bimolecular rate constant for the CH2OO + acetone reaction is measured to be (4.1 ± 0.4) × 10-13 cm3 s-1, consistent with previous measurements. The reactions of CH2OO with the ß-diketones acetylacetone and 3,3-dimethyl-2,5-pentanedione are found to have broadly similar rate constants of (6.6 ± 0.7) × 10-13 and (3.5 ± 0.8) × 10-13 cm3 s-1, respectively; these values may be cautiously considered as upper limits. In contrast, α-diketones react significantly faster, with rate constants of (1.45 ± 0.18) × 10-11 and (1.29 ± 0.15) × 10-11 cm3 s-1 measured for biacetyl and acetylpropionyl. The potential energy surfaces for these 1,3-dipolar cycloaddition reactions are characterized at the M06-2X/aug-cc-pVTZ and CBS-QB3 levels of theory and provide additional support to the observed experimental trends. The reactivity of carbonyl compounds with CH2OO is also interpreted by application of frontier molecular orbital theory and predicted using Hammett substituent constants. Finally, the results are compared with other kinetic studies of Criegee intermediate reactions with carbonyl compounds and discussed within the context of their atmospheric relevance.

Mode-specific vibrational predissociation dynamics of (HCl)2 via the free and bound HCl stretch overtones.

Velocity-map ion imaging has been used to study the vibrational predissociation dynamics of the HCl dimer following infrared (IR) excitation in the HCl stretch overtone region near 1.77 Å. HCl monomer predissociation products were detected state-selectively using 2 + 1 resonance-enhanced multiphoton ionization spectroscopy. The IR action spectrum shows the free HCl stretch (2ν1), the bound HCl stretch (2ν2), and a combination band involving the intermolecular van der Waals stretching mode (2ν2 + ν4). Fragment speed distributions extracted from ion images obtained for a range of HCl(v = 0, 1; J) levels following vibrational excitation on the 2ν1 and 2ν2 bands yield the correlated product pair distributions. All product pairs comprise HCl(v = 1) + HCl(v = 0) and show a strong propensity to minimize the recoil kinetic energy. Highly non-statistical and mode-dependent HCl product rotational distributions are observed, in contrast to that observed following stretch fundamental excitation. Predissociation lifetimes are also mode-dependent: excitation of the free HCl leads to τVP = 13 ± 1 ns, while the bound stretch has a shorter lifetime τVP ≤ 6 ns. The dimer dissociation energy determined from energy conservation (D0 = 397 ± 7 cm-1) is slightly smaller than the previously reported values. The results are discussed in the context of previous observations for (HF)2 and (HCl)2 after excitation of HX stretch fundamentals and models for vibrational predissociation.

UV photofragmentation dynamics of acetaldehyde cations prepared by single-photon VUV ionization.

Acetaldehyde cations (CH3CHO+) were prepared using single-photon vacuum ultraviolet ionization of CH3CHO in a molecular beam and the fragmentation dynamics explored over the photolysis wavelength range 390-210 nm using velocity-map ion imaging and photofragment yield (PHOFY) spectroscopy. Four fragmentation channels are characterized: CH3CHO+→ C2H3O+ + H (I), CH3CHO+→ HCO+ + CH3 (II), CH3CHO+→ CH3+ + HCO (III), CH3CHO+→ CH4+ + CO (IV). Channels (I), (II), and (IV) are observed across the full photolysis wavelength range while channel (III) is observed only at λ < 317 nm. Maximum fragment ion yields are obtained at ∼250 nm. Ion images were recorded over the range 316-228 nm, which corresponds to initial excitation to the B[combining tilde]2A' and C[combining tilde]2A' states of CH3CHO+. The speed and angular distributions are distinctly different for each detected ion and show evidence of both statistical and dynamical fragmentation pathways. At longer wavelengths, fragmentation via channel (I) leads to modest translational energies (ET), consistent with dissociation over a small barrier and production of highly internally excited CH3CO+. Additional components with EINT greater than the CH3CO+ secondary dissociation threshold appear at shorter wavelengths and are assigned to fragmentation products of vinyl alcohol cation or oxirane cation formed by isomerization of energized CH3CHO+. The ET distribution observed for channel (III) products peaks at zero but is notably colder than that predicted by phase space theory, particularly at longer photolysis wavelengths. The colder-than-statistical ET distributions are attributed to contributions from secondary fragmentation of energized CH3CO+ formed via channel (I), which are attenuated by CH3CHO+ isomerization at shorter wavelengths. Fragmentation via channels (II) and (IV) results in qualitatively similar outcomes, with evidence of isotropic statistical components at low-ET and anisotropic components due to excited state dynamics at higher ET.

Photodissociation dynamics of acetone studied by time-resolved ion imaging and photofragment excitation spectroscopy.

The photodissociation dynamics of acetone has been investigated using velocity-map ion imaging and photofragment excitation (PHOFEX) spectroscopy across a range of wavelengths spanning the first absorption band (236-308 nm). The radical products of the Norrish Type I dissociation, methyl and acetyl, as well as the molecular product ketene have been detected by single-photon VUV ionization at 118 nm. Ketene appears to be formed with non-negligible yield at all wavelengths, with a maximum value of Φ ≈ 0.3 at 280 nm. The modest translational energy release is inconsistent with dissociation over high barriers on the S0 surface, and ketene formation is tentatively assigned to a roaming pathway involving frustrated dissociation to the radical products. Fast-moving radical products are detected at λ ≤ 305 nm with total translational energy distributions that extend to the energetic limit, consistent with dissociation occurring near-exclusively on the T1 surface following intersystem crossing. At energies below the T1 barrier a statistical component indicative of S0 dissociation is observed, although dissociation via the S1/S0 conical intersection is absent at shorter wavelengths, in contrast to acetaldehyde. The methyl radical yield is enhanced over that of acetyl in PHOFEX spectra at λ ≤ 260 nm due to the onset of secondary dissociation of internally excited acetyl radicals. Time-resolved ion imaging experiments using picosecond duration pulses at 266 nm find an appearance time constant of τ = 1490 ± 140 ps for CH3 radicals formed on T1. The associated rate is representative of S1 → T1 intersystem crossing. At 284 nm, CH3 is formed on T1 with two distinct timescales: a fast <10 ns component is accompanied by a slower component with τ = 42 ± 7 ns. A two-step mechanism involving fast internal conversion, followed by slower intersystem crossing (S1 → S0 → T1) is proposed to explain the slow component.

Kinetics of the Reactions between the Criegee Intermediate CH2OO and Alcohols.

Reactions of the simplest Criegee intermediate (CH2OO) with a series of alcohols have been studied in a flash photolysis flow reactor. Laser photolysis of diiodomethane at 355 nm in the presence of molecular oxygen was used to produce CH2OO, and the absolute number densities were determined as a function of delay time from analysis of broadband transient absorption spectra obtained using a pulsed LED. The kinetics for the reactions of CH2OO with methanol, ethanol, and 2-propanol were measured under pseudo-first-order conditions at 295 K, yielding rate constants of (1.4 ± 0.4) × 10-13 cm3 s-1, (2.3 ± 0.6) × 10-13 cm3 s-1, and (1.9 ± 0.5) × 10-13 cm3 s-1, respectively. Complementary ab initio calculations were performed at the CCSD(T)/aug-cc-pVTZ//CCSD/cc-pVDZ level of theory to characterize stationary points on the reaction enthalpy and free energy surfaces and to elucidate the thermochemistry and mechanisms. The reactions proceed over free energy barriers of ∼8 kcal mol-1 to form geminal alkoxymethyl hydroperoxides: methoxymethyl hydroperoxide (MMHP), ethoxymethyl hydroperoxide (EMHP), and isopropoxymethyl hydroperoxide (PMHP). The experimental and theoretical results are compared to reactions of CH2OO with other hydroxylic compounds, such as water and carboxylic acids, and trends in reactivity are discussed.

Competing pathways in the near-UV photochemistry of acetaldehyde.

Time-resolved ion imaging measurements have been performed to explore the photochemistry of acetaldehyde at photolysis wavelengths spanning the range 265-328 nm. Ion images recorded probing CH3 radicals with single-photon VUV ionization show different dissociation dynamics in three distinct wavelength regions. At the longest photolysis wavelengths, λ > 318 nm, CH3 radicals are formed over tens of nanoseconds with a speed distribution that is consistent with statistical unimolecular dissociation on the S0 surface following internal conversion. In the range 292 nm ≤ λ ≤ 318 nm, dissociation occurs almost exclusively on the T1 surface following intersystem crossing and passage over a barrier, leading to the available energy being partitioned primarily into photofragment recoil. The CH3 speed distributions become bimodal at λ < 292 nm. In addition to the translationally fast T1 products, a new translationally slow, but non-statistical, component appears and grows in importance as the photolysis wavelength is decreased. Photofragment excitation (PHOFEX) spectra of CH3CHO obtained probing CH3 and HCO products are identical across the absorption band, indicating that three-body fragmentation is not responsible for the non-statistical slow component. Rather, translationally slow products are attributed to dissociation on S0, accessed via a conical intersection between the S1 and S0 surfaces at extended C-C distances. Time-resolved ion images of CH3 radicals measured using a picosecond laser operating at a photolysis wavelength of 266 nm show that product formation on T1 and S0via the conical intersection occurs with time constants of 240 ps and 560 ps, respectively.

UV photodissociation dynamics of CHI2Cl and its role as a photolytic precursor for a chlorinated Criegee intermediate.

Photolysis of geminal diiodoalkanes in the presence of molecular oxygen has become an established route to the laboratory production of several Criegee intermediates, and such compounds also have marine sources. Here, we explore the role that the trihaloalkane, chlorodiiodomethane (CHI2Cl), may play as a photolytic precursor for the chlorinated Criegee intermediate ClCHOO. CHI2Cl has been synthesized and its UV absorption spectrum measured; relative to that of CH2I2 the spectrum is shifted to longer wavelength and the photolysis lifetime is calculated to be less than two minutes. The photodissociation dynamics have been investigated using DC slice imaging, probing ground state I and spin-orbit excited I* atoms with 2 + 1 REMPI and single-photon VUV ionization. Total translational energy distributions are bimodal for I atoms and unimodal for I*, with around 72% of the available energy partitioned in to the internal degrees of freedom of the CHICl radical product, independent of photolysis wavelength. A bond dissociation energy of D0 = 1.73 ± 0.11 eV is inferred from the wavelength dependence of the translational energy release, which is slightly weaker than typical C-I bonds. Analysis of the photofragment angular distributions indicate dissociation is prompt and occurs primarily via transitions to states of A'' symmetry. Complementary high-level MRCI calculations, including spin-orbit coupling, have been performed to characterize the excited states and confirm that states of A'' symmetry with highly mixed singlet and triplet character are predominantly responsible for the absorption spectrum. Transient absorption spectroscopy has been used to measure the absorption spectrum of ClCHOO produced from the reaction of CHICl with O2 over the range 345-440 nm. The absorption spectrum, tentatively assigned to the syn conformer, is at shorter wavelengths relative to that of CH2OO and shows far weaker vibrational structure.

Same-sex partner bereavement in older women: an interpretative phenomenological analysis.

OBJECTIVES: Due to the lack of existing literature, the current research explored experiences of same-sex partner bereavement in women over the age of 60. METHOD: Semi-structured interviews were conducted with eight women. Transcripts were analysed using interpretative phenomenological analysis. RESULTS: Three themes were identified which elaborated the experiences of older women who had lost a same-sex partner: (1) being left alone encapsulated feelings of isolation and exclusion; (2) navigating visibility centred on how homophobia led to a lack of recognition of the women's grief; and (3) finding new places to be authentic related women's need for new relationships in which they could be themselves. The findings indicate that existing models of partner bereavement may provide useful frameworks when seeking to understand the experiences of older women who have lost their same-sex partners. CONCLUSION: The findings indicate that in addition to the experiences of partner bereavement noted in research with heterosexual widows, older women who lose same-sex partners may face particular challenges, which can impact upon psychological well-being and adjustment to loss. These challenges appear to result from past and current homophobic and heterosexist attitudes within the UK culture. A range of interventions at individual, group, health service, and societal levels may be beneficial in improving the psychological well-being of older women who lose a same-sex partner.

Near-UV photodissociation dynamics of CH2I2.

The near-UV photodissociation dynamics of CH2I2 has been investigated using a combination of velocity-map (slice) ion imaging and ab initio calculations characterizing the excited states. Ground state I((2)P3/2) and spin-orbit excited I*((2)P1/2) atoms were probed using 2 + 1 resonance-enhanced multiphoton ionization (REMPI) or with single-photon VUV ionization. Two-color ion images were recorded at pump wavelengths of 355 nm, 266 nm and 248 nm, and one-color ion images at the REMPI wavelengths of ∼304 nm and ∼280 nm. Analysis of the ion images shows that, regardless of iodine spin-orbit state, ∼20% of the available energy is partitioned into translation E(T) at all excitation wavelengths indicating that the CH2I co-fragment is formed highly internally excited. The translational energy distributions comprise a slow, "statistical" component that peaks near zero and faster components that peak away from zero. The slow component makes an increasingly large contribution to the distribution as the excitation wavelength is decreased. The C-I bond dissociation energy of D0 = 2.155 ± 0.008 eV is obtained from the trend in the E(T) release of the faster components with increasing excitation energy. The I and I* ion images are anisotropic, indicating prompt dissociation, and are characterized by ß parameters that become increasingly positive with increasing E(T). The decrease in ß at lower translational energies can be attributed to deviation from axial recoil. MRCI calculations including spin-orbit coupling have been performed to identify the overlapping features in the absorption spectrum and characterize one-dimensional cuts through the electronically excited potential energy surfaces. The excited states are of significantly mixed singlet and triplet character. At longer wavelengths, excitation directly accesses repulsive states primarily of B1 symmetry, consistent with the observed 〈ß〉, while shorter wavelengths accesses bound states, also of B1 symmetry that are crossed by repulsive states.

Dynamics and spectroscopy of CH2OO excited electronic states.

The excited states of the Criegee intermediate CH2OO are studied in molecular dynamics simulations using directly potentials from multi-reference perturbation theory (MR-PT2). The photoexcitation of the species is simulated, and trajectories are propagated in time on the excited state. Some of the photoexcitation events lead to direct fragmentation of the molecule, but other trajectories describe at least several vibrations in the excited state, that may terminate by relaxation to the ground electronic state. Limits on the role of non-adiabatic contributions to the process are estimated by two different simulations, one that forces surface-hopping at potential crossings, and another that ignores surface hopping altogether. The effect of non-adiabatic transitions is found to be small. Spectroscopic implications and consequences for the interpretation of experimental results are discussed.

Decomposing the First Absorption Band of OCS Using Photofragment Excitation Spectroscopy.

Photofragment excitation spectra of carbonyl sulfide (OCS) have been recorded from 212-260 nm by state-selectively probing either electronically excited S((1)D) or ground state S((3)P) photolysis products via 2 + 1 resonance-enhanced multiphoton ionization. Probing the major S((1)D) product results in a broad, unstructured action spectrum that reproduces the overall shape of the first absorption band. In contrast, spectra obtained probing S((3)P) products display prominent resonances superimposed on a broad continuum; the resonances correspond to the diffuse vibrational structure observed in the conventional absorption spectrum. The vibrational structure is assigned to four progressions, each dominated by the C-S stretch, ν1, following direct excitation to quasi-bound singlet and triplet states. The S((3)PJ) products are formed with a near-statistical population distribution over the J = 2, 1, and 0 spin-orbit levels across the wavelength range investigated. Although a minor contributor to the S atom yield near the peak of the absorption cross section, the relative yield of S((3)P) increases significantly at longer wavelengths. The experimental measurements validate recent theoretical work characterizing the electronic states responsible for the first absorption band by Schmidt and co-workers.