Fatigue in children who have recently completed treatment for acute lymphoblastic leukemia: a longitudinal study.

BACKGROUND: This study examined fatigue in patients treated for childhood acute lymphoblastic leukemia (ALL) over a 2-year period (3- to 27-months post-treatment completion), from the perspective of children and parent caregivers, compared to a healthy comparison group. METHODS: Eighty-three patients (4-16 years at enrolment) and their parents, reported on the child's fatigue using the Pediatric Quality of Life Inventory- Multidimensional Fatigue Scale (PedsQL-MFS), at 3- 15- and 27-months post-treatment completion, and 53 healthy children and their parents reported on fatigue across the same timepoints. RESULTS: Parent proxy-reporting showed that parents of ALL patients reported more total fatigue than parents of the comparison group at all time points, with all subscales elevated (general, cognitive, and sleep/rest fatigue). In contrast, patient self-report of fatigue over this period differed from the comparison children for the general fatigue subscale only. Self-reported total fatigue was worse than the comparison group at the 27-month timepoint, with cognitive and sleep/rest fatigue symptoms contributing to this difference. Expected improvements in fatigue over time were not evident in either patient or parent report and no demographic risk factors were identified. Parents and children from both groups reported significantly more fatigue at all time points compared to commonly utilised normative population data. CONCLUSIONS: Patients treated for childhood ALL are impacted by fatigue symptoms in the post-treatment and early survivorship period. These findings highlight that patients in the 2-years following treatment require increased symptom surveillance and may benefit particularly from interventions that target cognitive and sleep/rest fatigue.

Atmospheric molecular blobs shape up circumstellar envelopes of AGB stars.

During their thermally pulsing phase, asymptotic giant branch (AGB) stars eject material that forms extended dusty envelopes1. Visible polarimetric imaging found clumpy dust clouds within two stellar radii of several oxygen-rich stars2-6. Inhomogeneous molecular gas has also been observed in multiple emission lines within several stellar radii of different oxygen-rich stars, including W Hya and Mira7-10. At the stellar surface level, infrared images have shown intricate structures around the carbon semiregular variable R Scl and in the S-type star π1 Gru11,12. Infrared images have also shown clumpy dust structures within a few stellar radii of the prototypical carbon AGB star IRC+10°216 (refs. 13,14), and studies of molecular gas distribution beyond the dust formation zone have also shown complex circumstellar structures15. Because of the lack of sufficient spatial resolution, however, the distribution of molecular gas in the stellar atmosphere and the dust formation zone of AGB carbon stars is not known, nor is how it is subsequently expelled. Here we report observations with a resolution of one stellar radius of the recently formed dust and molecular gas in the atmosphere of IRC+10°216. Lines of HCN, SiS and SiC2 appear at different radii and in different clumps, which we interpret as large convective cells in the photosphere, as seen in Betelgeuse16. The convective cells coalesce with pulsation, causing anisotropies that, together with companions17,18, shape its circumstellar envelope.

Growth rates of contract-reared versus home-reared replacement dairy heifers.

Successful heifer rearing is dependent on achieving optimal average daily gain (ADG) targets to calve for the first time at 24 months. Whilst dairy farmers internationally have traditionally managed their heifers on-farm to achieve these targets, recent dairy herd expansion within Europe has resulted in increased demand for labour-saving heifer-rearing strategies, such as off-farm contractrearing. However, loss of direct influence on the day-to-day management decisions affecting the ability of heifers to grow adequately to achieve this age of first calving may represent a potential barrier to uptake. Hence, the aim of this longitudinal observational study was to compare the growth rates of contract- vs home-reared heifers. Approximately 6 500 heifers from 120 commercial Irish dairy farms were enrolled in a 3-year study. For 65 of these farms, heifers were reared at a contract-rearing facility. For the remaining 55 farms, heifers were reared on their home farm. Over the course of 20 months from birth until precalving, heifers were examined and weighed at four farm visits. The relationship between several independent variables (farm type, herd size, heifer breed, economic breeding index (EBI) and health events) and ADG at different time points was investigated and analysed utilising linear mixed models. Overall ADG for heifers throughout the rearing period was 0.71 kg/day. There was a significant association between farm type and ADG for all five linear ADG models; home-reared heifers grew, on average, 0.025, 0.039, 0.11 and 0.059 kg/day more than contract-reared heifers between visit 1 and visit 4 (overall ADG), visit 1 and visit 2, visit 2 and visit 3 and visit 1 and visit 3, respectively. The occurrence of diarrhoea during farm visit 2 (median age 8.5 months) was associated with a significant reduction in ADG between visit 3 and visit 4. Calf-hood disease (diarrhoea, respiratory disease or navel ill) was not associated with the growth rate during any of the subsequent visit periods. While home-reared heifers had greater ADG during four of the five periods studied, median heifer ADG in both cohorts exceeded the minimum published target weight gains at each developmental stage required for heifers to reach puberty, conceive at 15 months and calve for the first time at 24 months. Importantly, there was wide variation both within enterprises and between farms. It was concluded that while the absolute difference in daily growth rates of home- and contract-reared heifers was minimal, when considered in the context of the entire heifer-rearing period, these growth rate differences have the potential to impact the future reproductive and milk production performance of heifers.

A survey of biosecurity and health management practices on Irish dairy farms engaged in contract-rearing.

A survey was conducted to investigate potential differences in biosecurity and health management practices on Irish dairy farms that sent their heifers for contract-rearing (source dairy farms, SDF; n = 62) and those rearing their own heifers (control farms, CF; n = 50). Participating farmers were surveyed by postal questionnaire between September and November 2018. The overall response rate was 93%. Results show that structurally, SDF were larger, less fragmented, and more specialized than CF. Outsourcing of labor-intensive activities to external contractors was more common among SDF than CF, exposing them to potentially increased biosecurity risks associated with animal movements, use of shared equipment, and increased frequency of farm visitors. The majority of SDF sent heifers to a single-origin rearing facility (70%), with heifers most commonly arriving at the rearing unit between 2 and 4 mo (53%) and returning to the dairy farm between 18 and 21 mo of age (56%). Despite the increased biosecurity risk associated with contract-rearing, implementation of disease prevention measures was not superior on SDF compared with CF. For both farm types, there was scope for improvement to visitor biosecurity protocols, quarantine procedures, colostrum feeding practices, and hygiene of calving areas. This research provides an overview of the demographics and farm management practices implemented by dairy farmers engaged in contract-rearing of replacement heifers, and will serve to inform farmers, veterinary advisors, and policy makers.

Perceived cancer-related pain and fatigue, information needs, and fear of cancer recurrence among adult survivors of childhood cancer.

OBJECTIVE: Pain and fatigue are under-researched late effects of childhood cancer and its treatment, and may be interpreted by survivors as indicating cancer recurrence. Moreover, unmet information needs for managing pain and fatigue may be related to fear of cancer recurrence. We investigated the complex relationships between perceived cancer-related pain and fatigue, unmet information needs for managing pain and fatigue, and fear of cancer recurrence. METHODS: We surveyed 404 adult survivors of any form of childhood cancer (M = 16.82 years since treatment completion). RESULTS: Many survivors reported perceived cancer-related pain (28.7%) and fatigue (40.3%), and anticipated future pain (19.3%) and fatigue (26.2%). These symptomologies were all related to unmet information needs for managing pain (18.8%) and fatigue (32.2%; all p's<.001). Survivors reporting unmet information needs for managing pain (B = .48, 95% CI = 0.19-0.76, p = .001) and fatigue (B = .32, 95% CI = 0.06-0.52, p = .015) reported higher fear of cancer recurrence than survivors reporting no information needs. CONCLUSION: Survivors often have unmet information needs for managing pain and fatigue, and these unmet needs are related to fear of cancer recurrence. PRACTICE IMPLICATIONS: Long-term follow-up clinics should assess pain and fatigue. Information provision about pain and fatigue may be an important tool to help manage fear of cancer recurrence.

Circumstellar chemistry of Si-C bearing molecules in the C-rich AGB star IRC+10216.

Silicon carbide together with amorphous carbon are the main components of dust grains in the atmospheres of C-rich AGB stars. Small gaseous Si-C bearing molecules (such as SiC, SiCSi, and SiC2) are efficiently formed close to the stellar photosphere. They likely condense onto dust seeds owing to their highly refractory nature at the lower temperatures (i.e., below about 2500 K) in the dust growth zone which extends a few stellar radii from the photosphere. Beyond this region, the abundances of Si-C bearing molecules are expected to decrease until they are eventually reformed in the outer shells of the circumstellar envelope, owing to the interaction between the gas and the interstellar UV radiation field. Our goal is to understand the time-dependent chemical evolution of Si-C bond carriers probed by molecular spectral line emission in the circumstellar envelope of IRC+10216 at millimeter wavelengths.

Discovery of methyl silane and confirmation of silyl cyanide in IRC +10216.

We report the discovery in space of methyl silane, CH3SiH3, from observations of ten rotational transitions between 80 and 350 GHz (Ju from 4 to 16) with the IRAM 30 m radio telescope. The molecule was observed in the envelope of the C-star IRC +10216. The observed profiles and our models for the expected emission of methyl silane suggest that the it is formed in the inner zones of the circumstellar envelope, 1-40 R*, with an abundance of (0.5-1) × 10-8 relative to H2. We also observed several rotational transitions of silyl cyanide (SiH3CN), confirming its presence in IRC +10216 in particular, and in space in general. Our models indicate that silyl cyanide is also formed in the inner regions of the envelope, around 20 R*, with an abundance relative to H2 of 6×10-10. The possible formation mechanisms of both species are discussed. We also searched for related chemical species but only upper limits could be obtained.

The growth of carbon chains in IRC +10216 mapped with ALMA.

Linear carbon chains are common in various types of astronomical molecular sources. Possible formation mechanisms involve both bottom-up and top-down routes. We have carried out a combined observational and modeling study of the formation of carbon chains in the C-star envelope IRC +10216, where the polymerization of acetylene and hydrogen cyanide induced by ultraviolet photons can drive the formation of linear carbon chains of increasing length. We have used ALMA to map the emission of λ 3 mm rotational lines of the hydrocarbon radicals C2H, C4H, and C6H, and the CN-containing species CN, C3N, HC3N, and HC5N with an angular resolution of ~1″. The spatial distribution of all these species is a hollow, 5-10″ wide, spherical shell located at a radius of 10-20″ from the star, with no appreciable emission close to the star. Our observations resolve the broad shell of carbon chains into thinner sub-shells which are 1-2″ wide and not fully concentric, indicating that the mass loss process has been discontinuous and not fully isotropic. The radial distributions of the species mapped reveal subtle differences: while the hydrocarbon radicals have very similar radial distributions, the CN-containing species show more diverse distributions, with HC3N appearing earlier in the expansion and the radical CN extending later than the rest of the species. The observed morphology can be rationalized by a chemical model in which the growth of polyynes is mainly produced by rapid gas-phase chemical reactions of C2H and C4H radicals with unsaturated hydrocarbons, while cyanopolyynes are mainly formed from polyynes in gas-phase reactions with CN and C3N radicals.

Infancy and pediatric cancer: an exploratory study of parent psychological distress.

BACKGROUND: Research on the psychological experiences of parents of infants within pediatric oncology is sparse. This study examined rates and indicative risk factors for psychological distress in parents where there is either an infant patient or infant sibling of a patient. METHODS: Participants were mothers (n = 41) and fathers (n = 25) of infants under 2 years who either had a cancer diagnosis (n = 37; infant patients) or was an infant sibling of an older child with cancer (n = 29; infant siblings) recruited from a single oncology center. There were 21 couple dyads. Parents completed the Depression Anxiety Stress Scales short form and the Posttraumatic Stress Disorder Checklist. RESULTS: Mothers (47.5%) and fathers (37.5%) reported elevated, cancer-related posttraumatic stress symptoms. Rates of depression (12.2% of mothers and 12.0% of fathers) and anxiety symptoms (17.1% of mothers and 8.0% of fathers) were lower. Compared with parents of infant patients, parents of infant siblings reported significantly higher rates of depressive symptoms and trends toward higher rates of posttraumatic stress symptoms and anxiety symptoms. Parent anxiety was higher with increased time post diagnosis. No demographic or illness-related variables were associated with psychological distress, with the exception of the number of children in the family. CONCLUSIONS: Parent-child relationships are of fundamental importance during infancy. This study provides novel data highlighting the psychological impact for parents when a cancer diagnosis is made during this critical developmental period, including the contribution of family structure to parental distress. Results provide further support for applying a traumatic stress framework when exploring parent experiences of pediatric cancer. Copyright © 2016 John Wiley & Sons, Ltd.

High resolution spectroscopy of six SOCl2 isotopologues from the microwave to the far-infrared.

Despite its potential role as an atmospheric pollutant, thionyl chloride, SOCl2, remains poorly characterized in the gas phase. In this study, the pure rotational and ro-vibrational spectra of six isotopologues of this molecule, all detected in natural abundance, have been extensively studied from the cm-wave band to the far-infrared region by means of three complementary techniques: chirped-pulse Fourier transform microwave spectroscopy, sub-millimeter-wave spectroscopy using frequency multiplier chain, and synchrotron-based far-infrared spectroscopy. Owing to the complex line pattern which results from two nuclei with non-zero spins, new, high-level quantum-chemical calculations of the hyperfine structure played a crucial role in the spectroscopic analysis. From the combined experimental and theoretical work, an accurate semi-experimental equilibrium structure (r(e)(SE)) of SOCl2 has been derived. With the present data, spectroscopy-based methods can now be applied with confidence to detect and monitor this species, either by remote sensing or in situ.

The association of psychosocial screening and service provision in pediatric oncology: the Psychosocial Assessment Tool (PAT2.0) into clinical practice.

PURPOSE: Distress screening in oncology has been widely endorsed in recent years. However, current knowledge of the impact of screening on delivery of clinical psychosocial services is limited. This study investigated the association between screening and psychosocial services in the early period following diagnosis of childhood cancer. METHODS: The Psychosocial Assessment Tool (PAT2.0) was administered by clinical social workers in two pediatric oncology centers shortly following diagnosis. Psychosocial service activity in the first 8 weeks post diagnosis was collected via social work surveys and extraction of information from hospital databases. RESULTS: PAT2.0 and psychosocial service data were obtained for 89 families with a child newly diagnosed with cancer. Distribution of PAT2.0 risk categories was consistent with previous studies (57.3 % universal, 38.2 % targeted, 4.5 % clinical). Significant, weak to moderate correlations between PAT2.0 and social workers' estimates of psychosocial risk were observed. No significant differences in the amount of psychosocial services provided to families with "universal" versus "elevated" (i.e., targeted or clinical) risk were found. Number of days in hospital was strongly and positively associated with the amount of psychosocial services families received in the first 8 weeks following diagnosis. CONCLUSIONS: Psychosocial risk, as measured by the PAT2.0, and allocation of psychosocial services were not significantly associated in the early period following diagnosis. Further investigation is required to understand if differences emerge over time when psychosocial screening is implemented clinically. Development of clinical pathways of care needs to account for patients who may predominantly be treated in the outpatient setting.

Work-related stress and reward: an Australian study of multidisciplinary pediatric oncology healthcare providers.

OBJECTIVE: Managing staff stress and preventing long-term burnout in oncology staff are highly important for both staff and patient well-being. Research addressing work-related stress in adult oncology is well documented; however, less is known about this topic in the pediatric context. This study examined sources of work-related stress and reward specific to multidisciplinary staff working in pediatric oncology in Australia. METHOD: Participants were 107 pediatric oncology clinicians, including medical, nursing, and allied health staff from two Australian pediatric oncology centers. Participants completed an online survey using two newly developed measures: the work stressors scale-pediatric oncology and the work rewards scale-pediatric oncology. RESULTS: The most commonly reported sources of both stress and reward are related to patient care and interactions with children. Results indicated that levels of work-related stress and reward were similar between the professional disciplines and between the two hospitals. Regression analyses revealed no demographic or organizational factors that were associated with either stress or reward. CONCLUSIONS: Work-related stress and reward are not mutually exclusive; particular situations and events can be simultaneously stressful and rewarding for healthcare providers. Although patient care and interactions with children was found to be the most stressful aspect of working in this speciality, it was also the greatest source of reward. Results are discussed in relation to workplace approaches to staff well-being and stress reduction.

Early psychological reactions in parents of children with a life threatening illness within a pediatric hospital setting.

RESEARCH IN CONTEXT: Parents of children with life threatening illness or injuries are at elevated risk of distress reactions, involving symptoms of acute stress disorder, depression and anxiety. Currently, the impact of child illness factors is unclear, and to date research systematically examining the prevalence of these psychological reactions across different illness groups with an acute life threat is sparse. This is important to explore given that studies show that parent functioning impacts on the psychological adjustment and recovery of the ill child. WHAT DOES THIS STUDY ADD?: At four weeks following a child's diagnosis of a serious illness, 49-54% of parents met DSM-IV criteria for acute stress disorder, across a number of illness groups, whereas 15-27% of parents were in the moderate/severe range for depression and anxiety, and 25-31% for stress. Results from this study demonstrate that rates and severity of these psychological reactions in parents of seriously ill children do not vary according to illness type. BACKGROUND: A life threatening childhood illness/injury can lead to significant distress reactions in parents, with independent studies finding such reactions in several different illness groups. To date, there is limited research systematically comparing the prevalence of adverse parental psychological reactions across different childhood illness groups with an acute life threat. This study aimed to investigate the frequency and severity of symptoms of acute traumatic stress, depression, anxiety and general stress in parents, following admission of their child to hospital for a life threatening illness. The study also aimed to explore the relationship between these symptoms, and to determine whether they differ according to illness/injury. METHODS: Cross-sectional data from a prospective, longitudinal study are reported. Participants were 194 parents of 145 children (49 couples), admitted to cardiology (n=53), oncology (n=40) and pediatric intensive care units (n=52), for serious illnesses/injuries. Parents completed self-report questionnaires within four weeks of hospital admission. RESULTS: Rates of acute traumatic stress (P=0.262), depression (P=0.525), anxiety (P=0.453) and general stress symptoms (P=0.720) in parents were comparable across illness type, with 49-54% reaching criteria for acute stress disorder, 15-27% having clinical levels of depression and anxiety, and 25-31% for general stress. Anxiety was most strongly associated with acute traumatic stress (r=0.56), closely followed by stress (r=0.52) and depression (r=0.49), with all correlations highly significant (P<0.001). CONCLUSIONS: These findings provide evidence that the child's medical condition is not associated with parents' experience of clinically significant psychological symptoms, and emphasize the importance for health care providers to be aware of these potential psychological reactions in parents, regardless of the type of illness.

Discovery of SiCSi in IRC +10216: A missing link between gas and dust carriers of Si-C bonds.

We report the discovery in space of a disilicon species, SiCSi, from observations between 80 and 350 GHz with the IRAM 30m radio telescope. Owing to the close coordination between laboratory experiments and astrophysics, 112 lines have now been detected in the carbon-rich star CW Leo. The derived frequencies yield improved rotational and centrifugal distortion constants up to sixth order. From the line profiles and interferometric maps with the Submillimeter Array, the bulk of the SiCSi emission arises from a region of 6″ in radius. The derived abundance is comparable to that of SiC2. As expected from chemical equilibrium calculations, SiCSi and SiC2 are the most abundant species harboring a Si-C bond in the dust formation zone and certainly both play a key role in the formation of SiC dust grains.

Parent perceptions of managing child behavioural side-effects of cancer treatment: a qualitative study.

BACKGROUND: Very little research has examined the role of parenting in managing behavioural side-effects of cancer treatment. The purpose of this paper was to explore parent perceptions of (a) parenting in the context of childhood cancer; (b) the parenting strategies used in the context of managing child behavioural side-effects of cancer treatment; and (c) the perceived impact that cancer-specific parenting strategies have on child behaviour. METHODS: Participants were 15 mothers of children aged 2-6 years in the maintenance phase of treatment for acute lymphoblastic leukaemia at the Royal Children's Hospital Children's Cancer Centre, Melbourne, Australia. Mothers participated in a one-on-one semi-structured telephone interview using an interview guide which included questions on parenting in the context of childhood cancer, specifically in relation to behavioural side-effects (problems with behaviour, sleep and eating) and any perceived impact cancer-specific parenting may have on the ill child. RESULTS: Many parents reported that following their child's cancer diagnosis, they had to implement a suite of 'new' strategies that 'pre-diagnosis' were used only in moderation, if at all. The most salient theme that emerged was parents' perception that their parenting became more lax since their child's diagnosis. Parents further reported specific parenting strategies for each of the main child behavioural side-effects of cancer treatment. CONCLUSION: Data from the current qualitative exploratory study highlight the role of specific parenting strategies in managing or assisting child behavioural side-effects of cancer treatment. Further quantitative research is needed to more fully examine the association between parenting and child behavioural outcomes in order to develop modifiable approaches to improving child behavioural side-effects in a paediatric oncology context.

Optical spectra of the silicon-terminated carbon chain radicals SiCnH (n = 3,4,5).

The gas-phase optical spectra of three silicon-terminated carbon chain radicals, SiCnH (n = 3 - 5), formed in a jet-cooled discharge of silane and acetylene, have been investigated by resonant two-color two-photon ionization and laser-induced fluorescence/dispersed fluorescence. Analysis of the spectra was facilitated by calculations performed using equation-of-motion coupled cluster methods. For SiC3H and SiC5H, the observed transitions are well-described as excitations from a (2)Π ground state to a (2)Σ state, in which vibronic coupling, likely involving a higher-lying Π state with a very large predicted f-value (close to unity), is persistent. The lowest (2)Σ states of both species are characterized by a rare silicon triple bond, which was identified previously [T. C. Smith, H. Y. Li, D. J. Clouthier, C. T. Kingston, and A. J. Merer, J. Chem. Phys. 112, 3662 (2000)] in the lowest (2)Σ state of SiCH. Although a strong Π - Π transition is predicted for SiC4H, the observed spectrum near 505 nm more likely corresponds to excitation to a relatively dark Σ state which is vibronically coupled to a nearby Π state. In contrast to the chains with an odd number of carbon atoms, which exhibit relatively sharp spectral features and lifetimes in the 10-100 ns range, SiC4H shows intrinsically broadened spectral features consistent with a ∼100 fs lifetime, and a subsequent long-lived decay (>50 µs) which we ascribe to mixing with a nearby quartet state arising from the same electronic configuration. The spin-orbit coupling constants for both SiC3H and SiC5H radicals were determined to be approximately 64 cm(-1), similar to that of SiCH (69.8 cm(-1)), suggesting that the unpaired electron in these species is localized on the silicon atom. Motivated by the new optical work, the rotational spectrum of linear SiC3H was detected by cavity Fourier-transform microwave spectroscopy in the 13-34 GHz range. Each rotational transition from the [Formula: see text] ground state exhibits well-resolved Λ-doubling and hyperfine structure; the derived rotational constant of B = 2.605 GHz is in excellent agreement with our calculations.

Filtration effectiveness of HVAC systems at near-roadway schools.

UNLABELLED: Concern for the exposure of children attending schools located near busy roadways to toxic, traffic-related air pollutants has raised questions regarding the environmental benefits of advanced heating, ventilation, and air-conditioning (HVAC) filtration systems for near-road pollution. Levels of black carbon and gaseous pollutants were measured at three indoor classroom sites and at seven outdoor monitoring sites at Las Vegas schools. Initial HVAC filtration systems effected a 31-66% reduction in black carbon particle concentrations inside three schools compared with ambient air concentrations. After improved filtration systems were installed, black carbon particle concentrations were reduced by 74-97% inside three classrooms relative to ambient air concentrations. Average black carbon particle concentrations inside the schools with improved filtration systems were lower than typical ambient Las Vegas concentrations by 49-96%. Gaseous pollutants were higher indoors than outdoors. The higher indoor concentrations most likely originated at least partially from indoor sources, which were not targeted as part of this intervention. PRACTICAL IMPLICATIONS: Recent literature has demonstrated adverse health effects in subjects exposed to ambient air near major roadways. Current smart growth planning and infill development often require that buildings such as schools are built near major roadways. Improving the filtration systems of a school's HVAC system was shown to decrease children's exposure to near-roadway diesel particulate matter. However, reducing exposure to the gas-phase air toxics, which primarily originated from indoor sources, may require multiple filter passes on recirculated air.

The electronic spectrum of Si3 I: triplet D(3h) system.

We report the measurement of a jet-cooled electronic spectrum of the silicon trimer. Si(3) was produced in a pulsed discharge of silane in argon, and the excitation spectrum examined in the 18 000-20 800 cm(-1) region. A combination of resonant two-color two-photon ionization (R2C2PI) time-of-flight mass spectroscopy, laser-induced fluorescence/dispersed fluorescence, and equation-of-motion coupled-cluster calculations have been used to establish that the observed spectrum is dominated by the 1(3)A(1)" - ã (3)A(2)' transition of the D(3h) isomer. The spectrum has an origin transition at 18,600 ± 4 cm(-1) and a short progression in the symmetric stretch with a frequency of ∼445 cm(-1), in good agreement with a predicted vertical transition energy of 2.34 eV for excitation to the 1(3)A(1)" state, which has a calculated symmetric stretching frequency of 480 cm(-1). In addition, a ∼505 cm(-1) ground state vibrational frequency determined from sequence bands and dispersed fluorescence is in agreement with an earlier zero-electron kinetic energy study of the lowest D(3h) state and with theory. A weaker, overlapping band system with a ∼360 cm(-1) progression, observed in the same mass channel (m/z = 84) by R2C2PI but under different discharge conditions, is thought to be due to transitions from the (more complicated) singlet C(2v) ground state ((1)A(1)) state of Si(3). Evidence of emission to this latter state in the triplet dispersed fluorescence spectra suggests extensive mixing in the excited triplet and singlet manifolds. Prospects for further spectroscopic characterization of the singlet system and direct measurement of the energy separation between the lowest singlet and triplet states are discussed.

The pure rotational spectrum of HPS (X̃1A'): chemical bonding in second-row elements.

The pure rotational spectrum of HPS, as well as its (34)S and D isotopologues, has been recorded at microwave, millimeter, and submillimeter wavelengths, the first observation of this molecule in the gas phase. The data were obtained using a combination of millimeter direct absorption, Fourier transform microwave (FTMW), and microwave-microwave double-resonance techniques, which cover the total frequency range from 15 to 419 GHz. Quantum chemical calculations at the B3LYP and CCSD(T) levels were also performed to aid in spectral identification. HPS was created in the direct absorption experiment from a mixture of elemental phosphorus, H(2)S, and Ar carrier gas; DPS was produced by adding D(2). In the FTMW study, these species were generated in a pulsed discharge nozzle from PH(3) and H(2)S or D(2)S, diluted in neon. The spectra recorded for HPS and its isotopologues exhibit clear asymmetric top patterns indicating bent structures; phosphorus hyperfine splittings were also observed in HPS, but not DPS. Analysis of the data yielded rotation, centrifugal distortion, and phosphorus nuclear spin-rotation parameters for the individual species. The r(m) ((1)) structure for HPS, calculated from the rotational constants, is r(H-P) = 1.438(1) Å, r(P-S) = 1.9320(1) Å, and θ(H-P-S) = 101.85(9)°. Empirically correcting for zero-point vibrational effects yields the geometry r(e)(H-P) = 1.4321(2) Å, r(e)(P-S) = 1.9287(1) Å, and θ(e)(H-P-S) = 101.78(1)°, in close agreement with the r(m) ((1)) structure. A small inertial defect was found for HPS indicating a relatively rigid molecule. Based on these data, the bonding in this species is best represented as H-P=S, similar to the first-row analog HNO, as well as HNS and HPO. Therefore, substitution of phosphorus and sulfur for nitrogen and oxygen does not result in a dramatic structural change.