Analysis on high-resolution spectrum of the S1-S0 transition of free-base phthalocyanine.

A high-resolution absorption spectrum of the S1-S0 transition of free-base phthalocyanine was observed and analyzed with improved reliability. The spectrum, with a partially resolved rotational structure, was obtained by using the buffer-gas cooling technique and a single-mode tunable laser. Our new analysis reveals that the S1←S0000 band belongs to the a-type transition, where the electronic transition moment aligns parallel to the NH-HN direction, allowing the assignment of the S1 state to 1B3u. These results agree with a prior study using supersonic expansion and are well supported by theoretical calculations. Interestingly, the rotational constant B in the S1 state, which is often smaller than that in the ground state for typical molecules, was found to be slightly larger than that in the S01Ag state. This suggests a change in the character of π bonds with the electronic excitation.

Newly observed low-lying Ω = 1 state of PbO.

High-resolution spectroscopy of lead monoxide was performed in a range of 22 400-25 300 cm-1. A new Ω = 1 state located between the a1 and A0+ states was observed, and it is labeled c1. Spectroscopic constants, including the hyperfine interaction coefficient, were determined for the a1 and c1 states. The vibrational levels of these two electronic states are located closely to each other, and the interaction between them causes gradual exchange of electronic state properties in our observation wave number range. Our observation poses a question for the band assignment for the b0- state, which has some resemblance with this c1 state.

Enhancement of a pyroelectric body energy harvesting scheme employing pulsed electric fields.

This research utilizes waste heat energy as a sustainable energy source to enhance pyroelectric power output by combining pyroelectric nanogenerators with an external pulsed electric field. When the surface temperature of the pyroelectric body varies, applying different pulses of the external electric field results in maximum power accumulation. A novel power-generating experimental setup was developed to measure and compute pyroelectric power generation. A standard Fuji ceramic C-9 sample was used to generate pyroelectric energy in a 20 °C temperature range from 120 to 140 °C. The continuous temperature variation frequency was 0.05 Hz, and the pulsed electric field was applied when the temperature rose. Pulses of the electric field with widths of 10, 50, 100, and 200 ms were applied to the sample under different pulse amplitudes, and the amplitude of each pulse was 250, 500, 1000, or 1500 V/mm. The maximum power generated through the application of an external pulsed electric field under the above-mentioned conditions was evaluated. This system had the highest power density of 0.204 mJ cm-2 °C-1 kV-1. In addition, for the lowest input power, the maximum power generation condition was a 10 ms pulse width and an amplitude of 250 V mm-1 in the applied electric field. This state might power smart sensor modules, IoT devices, automobiles, and other waste heat energy applications. Nano-pulse electric field applications may reduce input power to its lowest level, dependent on net-producing power. Therefore, new researchers can use net-generation power efficiency to create a large-scale power source using multiple pyroelectric arrays.

Doppler-free Spectroscopy of Buffer-Gas-Cooled Calcium Monohydroxide.

In this study, we report the Doppler-free spectra of buffer-gas-cooled CaOH. We observed five Doppler-free spectra containing low-J Q1 and R12 transitions, which were only partially resolved by previous Doppler-limited spectroscopies. The spectra frequencies were corrected using the Doppler-free spectra of iodine molecules; accordingly, the uncertainty was estimated to be below 10 MHz. We determined the spin-rotation constant in the ground state, which agrees with the values reported in the literature obtained based on millimeter-wave data within 1 MHz. This suggests that the relative uncertainty is much smaller. The present study demonstrates the Doppler-free spectroscopy of a polyatomic radical and the broad applicability of the buffer gas cooling method to molecular spectroscopy. CaOH is the only polyatomic molecule that can be directly laser-cooled and trapped in a magneto-optical trap. High-resolution spectroscopy of such molecules is useful for establishing efficient laser cooling schemes of polyatomic molecules.

Direct Elucidation of the Vibrationally Averaged Structure of Benzene: A Path Integral Molecular Dynamics Study.

Path integral molecular dynamics (PIMD) simulations for C6H6, C6D6, and C6T6 have been carried out to directly estimate the distribution of projected C-H(D,T) bond lengths onto the principal axis plane. The average values of raw C-H(D,T) bond lengths obtained from PIMD simulations are in the order of ⟨RC-H⟩ > ⟨RC-D⟩ > ⟨RC-T⟩ due to the anharmonicity of the potential energy curve. However, the projected C-H(D,T) bond lengths are almost the same as those reported by Hirano et al. [J. Mol. Struct. 2021, 1243, 130537]. Our PIMD simulations directly and strongly support the explanation by Hirano et al. for the experimental observations that almost the same projected C-H(D) bond lengths are found for C6H6 and C6D6. The PIMD simulations also predicted the same projected bond lengths for C6T6 as those of C6H(D)6. In addition to the previous local mode analysis, the present PIMD simulations predicted, for benzene isotopologues, that the vibrationally averaged structure is planar but non-flat.

Electronic, vibrational, and rotational analysis of 1,2-benzanthracene by high-resolution spectroscopy referenced to an optical frequency comb.

The electronic and vibrational structures of 1,2-benzanthracene-h12 (aBA-h12) and 1,2-benzanthracene-d12 (aBA-d12) were elucidated by analyzing fluorescence excitation spectra and dispersed fluorescence spectra in a supersonic jet on the basis of DFT calculation. We also observed the high-resolution and high-precision fluorescence excitation spectrum of the S1←S000 0 band, and determined the accurate rotational constants in the zero-vibrational levels of the S0 and S1 states. In this high-resolution measurement, we used a single-mode UV laser whose frequencies were controlled with reference to an optical frequency comb. The inertial defect is negligibly small, the molecule is considered to be planar, and the obtained rotational constants were well reproduced by the equation-of-motion coupled cluster singles and doubles (EOM-CCSD) calculation. Both a-type and b-type transitions are found to be included in the rotationally resolved spectrum, and the a-type contribution is dominant, that is, the transition moment is nearly parallel to the long axis of the aBA molecule. We concluded that the S1 state is mainly composed of the Φ(B) configuration. The observed fluorescence lifetime (106 ns) is considerably longer than that of the Φ(A) system, such as anthracene (18 ns). The transition moment for the lower state of mixed states becomes small, reflecting a near-cancelation of the contributions from the parts of the wavefunction corresponding to the two electronic configurations. The bandwidth of the S2 ← S0 transition is large, and the structure is complicated. It is attributed to vibronic coupling with the high vibrational levels of the S1 state.

Infrared and Laser-Induced Fluorescence Spectra of Sumanene Isolated in Solid para-Hydrogen.

The para-hydrogen (p-H2) matrix-isolation technique has been scarcely used to record electronic absorption and emission spectra. It is expected that its small matrix shifts due to diminished molecular interactions and the softness of the lattice might be advantageous to help identify the carriers of the diffuse interstellar bands. In this article, we present infrared, fluorescence excitation, and dispersed fluorescence spectra of sumanene (C21H12), a bowl-shaped polycyclic aromatic hydrocarbon and a fragment of C60, isolated in solid p-H2. The recorded vibrational wavenumbers from infrared and dispersed fluorescence agree with the scaled harmonic vibrational wavenumbers calculated with the B3PW91/6-311++G(2d,2p) and B3LYP/6-311++G(2d,2p) methods. The recorded fluorescence excitation spectra are consistent with the spectra of jet-cooled gas-phase C21H12 reported previously by Kunishige et al. We found a rather small matrix shift of 55 cm-1 for the S1-S0 electronic transition origin located at 27 888 cm-1. Vibrational wavenumbers associated with the S1 state of C21H12 inferred from the experimental spectrum can be assigned mostly to fundamental normal modes; they are in satisfactory agreement with scaled harmonic vibrational wavenumbers calculated at the TD-B3PW91/6-311++G(2d,2p) level of theory. Significantly more vibrational modes of the S1 state were identified as compared with those in the reported gas-phase work. The potential of p-H2 matrix-isolation spectroscopy to provide electronic excitation spectra suitable for comparison to astronomical observations is discussed by comparing the spectra of C21H12 isolated in solid p-H2 and in solid Ne, a matrix host commonly employed in astrochemistry.

High-resolution spectroscopy of buffer-gas-cooled phthalocyanine.

For over five decades, studies in the field of chemical physics and physical chemistry have primarily aimed to understand the quantum properties of molecules. However, high-resolution rovibronic spectroscopy has been limited to relatively small and simple systems because translationally and rotationally cold samples have not been prepared in sufficiently large quantities for large and complex systems. In this study, we present high-resolution rovibronic spectroscopy results for large gas-phase molecules, namely, free-base phthalocya-nine (FBPc). The findings suggest that buffer-gas cooling may be effective for large molecules introduced via laser ablation. High-resolution electronic spectroscopy, combined with other experimental and theoretical studies, will be useful in understanding the quantum properties of molecules. These findings also serve as a guide for quantum chemical calculations of large molecules.

Non-contact and direct electrocaloric effect measurement for high-throughput material screening.

A non-contact and direct electrocaloric effect (ECE) measurement system was developed for rapid ECE measurement. The ECE of ferroelectric materials was measured directly using two measurement methods, namely, the constant heating rate method (CH method) and one-dimensional temperature gradient method (1D method), with the measurement system. The CH method continuously measures the ECE while gently heating the sample, and it can evaluate the performance of the sample more quickly than conventional methods that measure the ECE at steady state. The 1D method directly measures the ECE using a 1D temperature distribution applied to the sample. This method can measure the temperature dependence of the ECE faster than the CH method. The measurement system achieved a high signal-to-noise ratio, and the temperature dependence of the ECE measured by the two methods was consistent. The proposed measurement system and methods enable promising candidate materials for electrocaloric cooling systems to be screened more rapidly than when using conventional approaches.

Electronic and vibrational structure in the S0 and S1 states of corannulene.

Corannulene is a nonplanar aromatic hydrocarbon also known as a buckybowl. Its electronic and vibrational structure has been investigated by analyzing its fluorescence excitation spectrum and dispersed fluorescence spectrum in a supersonic jet. Its spectral features are in keeping with the expectation, confirmed by some previous results, that it has fivefold or C5v symmetry. The observed prominent vibronic bands in the S1 ← S0 transition have been assigned to e1 and e2 bands on the basis of theoretical calculations so that the S1 state was assigned to 1E2. The symmetry adapted cluster configuration interaction calculation supports this assignment of the S1 electronic state, although the time-dependent density functional theory calculation suggests that the S1 state is 1A2. It has also been shown that the normal coordinates for strong vibronic bands mainly include out-of-plane vibrational motion. The rotational envelopes are well explained by taking account of the Coriolis interaction between the degenerate vibrational and rotational levels. The mechanism of bowl-to-bowl inversion is also discussed with the results of theoretical calculations regarding the barrier to inversion and metastable conformation.

Infrared spectrum of hydrogenated corannulene rim-HC20H10 isolated in solid para-hydrogen.

Hydrogenated polycyclic aromatic hydrocarbons have been proposed to be carriers of the interstellar unidentified infrared (UIR) emission bands and the catalysts for formation of H2; spectral characterizations of these species are hence important. We report the infrared (IR) spectrum of mono-hydrogenated corannulene (HC20H10) in solid para-hydrogen (p-H2). In experiments of electron bombardment of a mixture of corannulene and p-H2 during deposition of a matrix at 3.2 K, two groups of spectral lines increased with time during maintenance of the matrix in darkness after deposition. Lines in one group were assigned to the most stable isomer of hydrogenated corannulene, rim-HC20H10, according to the expected chemistry and a comparison with scaled harmonic vibrational wavenumbers and IR intensities predicted with the B3PW91/6-311++G(2d,2p) method. The lines in the other group do not agree with predicted spectra of other HC20H10 isomers and remain unassigned. Alternative hydrogenation was achieved with H atoms produced photochemically in the infrared-induced reaction Cl + H2 (v = 1) → H + HCl in a Cl2/C20H10/p-H2 matrix. With this method, only lines attributable to rim-HC20H10 were observed, indicating that hydrogenation via a quantum-mechanical tunneling mechanism produces preferably the least-energy rim-HC20H10 regardless of similar barrier heights and widths for the formation of rim-HC20H10 and hub-HC20H10. The mechanisms of formation in both experiments are discussed. The bands near 3.3 and 3.4 µm of rim-HC20H10 agree with the UIR emission bands in position and relative intensity, but other bands do not match satisfactorily with the UIR bands.

Actual resuscitation actions after the training of chest compression-only CPR and AED use among new university students.

BACKGROUND: Although cardiopulmonary resuscitation (CPR) training is recommended in schools, there are few attempts to train all students at universities and no reports showing actual resuscitation actions at emergency settings after the training. We surveyed how many students encountered a collapsed person, whether they performed any resuscitation actions, and any reasons why they could not do any resuscitation actions. METHODS: We have provided chest compression-only CPR and automated external defibrillator (AED) use training for 3000 new university students every April since 2015 and followed up on their subsequent emergency actions to collapsed persons in the real world. We carried out a questionnaire survey for 2nd through 4th-year students during the annual student health checkup period in 2018. RESULTS: A total of 7595 students underwent the annual health checkup and 5549 of them (73.1%) responded to the survey. The rates of encountering collapsed persons and out-of-hospital cardiac arrest (OHCA) patients were 2.5 and 1.1 per 100 person-years, respectively. Of the 264 students who encountered a collapsed person, 82 (53.6%) who encountered non-OHCA collapsed persons and 54 (48.6%) who encountered OHCA persons performed at least one resuscitation action including either chest compression, AED use, or any other various resuscitation actions. CONCLUSIONS: The incidence rate of encountering OHCA patients was 1.1 per 100 person-years and half of them who encountered a collapsed person performed at least one resuscitation action. Hands-on mass training would encourage university students to perform any resuscitation actions on the emergency scene.

Electronic and vibrational structures in the S0 and S1 states of coronene.

We observed the fluorescence excitation spectra and dispersed fluorescence spectra of jet-cooled coronene-h12 and coronene-d12. We analyzed the vibronic structures, assuming a planar and sixfold symmetric molecular structure (D6h). The S1 state was identified to be B2u1. The S1B2u1←S0A1g1 transition is symmetry forbidden, so the 000 band is missing in the fluorescence excitation spectrum. We found a number of vibronic bands that were assigned to the e2g fundamental bands and their combination bands with totally symmetric a1g vibrations. This spectral feature is similar to that of benzene although several strong e2g bands are seen in coronene. The band shape (rotational envelope) was significantly different in each e2g mode. It was shown that degenerate rotational levels were shifted and split by the Coriolis interaction. We calculated the Coriolis parameter using the molecular structure in the S1 state and the normal coordinate of each e2g vibrational mode, which were obtained by theoretical calculations. The calculated band shapes well reproduced the observed ones, suggesting that the isolated coronene molecule has D6h symmetry.

Spectroscopic study on deuterated benzenes. I. Microwave spectra and molecular structure in the ground state.

We observed microwave absorption spectra of some deuterated benzenes and accurately determined the rotational constants of all H/D isotopomers in the ground vibrational state. Using synthetic analysis assuming that all bond angles are 120°, the mean bond lengths were obtained to be r0(C-C) = 1.3971 Å and r0(C-H) = r0(C-D) = 1.0805 Å. It has been concluded that the effect of deuterium substitution on the molecular structure is negligibly small and that the mean bond lengths of C-H and C-D are identical unlike small aliphatic hydrocarbons, in which r0(C-D) is about 5 mÅ shorter than r0(C-H). It is considered that anharmonicity is very small in the C-H stretching vibration of aromatic hydrocarbons.

Spectroscopic study on deuterated benzenes. III. Vibronic structure and dynamics in the S(1) state.

We observed the fluorescence excitation spectra and mass-selected resonance enhanced multiphoton ionization (REMPI) excitation spectra for the 6(0)(1), 6(0)(1)1(0)(1), and 6(0)(1)1(0)(2) bands of the S1←S0 transition of jet-cooled deuterated benzene and assigned the vibronic bands of C6D6 and C6HD5. The 6(0)(1)1(0)(n) (n = 0, 1, 2) and 0(0)(0) transition energies were found to be dependent only on the number of D atoms (ND), which was reflected by the zero-point energy of each H/D isotopomer. In some isotopomers some bands, such as those of out-of-plane vibrations mixed with 6(1)1(n), make the spectra complex. These included the 6(1)10(2)1(n) level or combination bands with ν12 which are allowed because of reduced molecular symmetry. From the lifetime measurements of each vibronic band, some enhancement of the nonradiative intramolecular vibrational redistribution (IVR) process was observed. It was also found that the threshold excess energy of "channel three" was higher than the 6(1)1(2) levels, which were similar for all the H/D isotopomers. We suggest that the channel three nonradiative process could be caused mainly by in-plane processes such as IVR and internal conversion at the high vibrational levels in the S1 state of benzene, although the out-of-plane vibrations might contribute to some degree.

Spectroscopic study on deuterated benzenes. II. High-resolution laser spectroscopy and rotational structure in the S(1) state.

High-resolution spectra of the S1←S0 transition in jet-cooled deuterated benzenes were observed using pulse dye amplification of single-mode laser light and mass-selective resonance enhanced multiphoton ionization (REMPI) detection. The vibrational and rotational structures were accurately analyzed for the vibronic levels in the S1 state. The degenerate 6(1) levels of C6H6 or C6D6 are split into 6a(1) and 6b(1) in many of deuterated benzenes. The rigid-rotor rotational constants were assessed and found to be slightly different between 6a and 6b because of different mean molecular structures. Their rotational levels are significantly shifted by Coriolis interactions. It was found that the Coriolis parameter proportionally changed with the number of substituted D atoms.

High-resolution laser spectroscopy and magnetic effect of the B̃2E' ← X̃2A2' transition of 14NO3 radical.

Rotationally resolved high-resolution fluorescence excitation spectra of (14)NO3 radical have been observed for the 662 nm band, which is assigned as the 0-0 band of the B̃(2)E' ←X̃(2)A2' transition, by crossing a single-mode laser beam perpendicularly to a collimated molecular beam. More than 3000 rotational lines were detected in 15,070-15,145 cm(-1) region, but it is difficult to find the rotational line series. Remarkable rotational line pairs, whose interval is about 0.0246 cm(-1), were found in the observed spectrum. This interval is the same amount with the spin-rotation splitting of the X̃(2)A2' (υ = 0, k = 0, N = 1) level. From this interval and the observed Zeeman splitting up to 360 G, seven line pairs were assigned as the transitions to the (2)E'(3/2) (J' = 1.5) levels and 15 line pairs were assigned as the transitions to the (2)E'(1/2) (J' = 0.5) levels. From the rotational analysis, we recognized that the (2)E' state splits into (2)E'(3/2) and (2)E'(1/2) by the spin-orbit interaction and the effective spin-orbit interaction constant was roughly estimated as -21 cm(-1). From the number of the rotational line pairs, we concluded that the complicated rotational structure of this 662 nm band of (14)NO3 mainly owes to the vibronic interaction between the B̃(2)E' state and the dark Ã(2)E″ state through the a2″ symmetry vibrational mode.

S1 and S2 states of linear and zigzag cata-condensed hydrocarbons.

We investigated the S1 and S2 states of linear and zigzag cata-condensed hydrocarbons on the basis of the results of jet spectroscopy and theoretical calculations. The S1 states of anthracene and tetracene are represented by the HOMO → LUMO configuration (Φ(A)), whereas those of phenanthrene and chrysene are represented by HOMO-1 → LUMO and HOMO → LUMO+1 configurations (Φ(B)). We found that the fluorescence lifetime varied with different vibronic levels in the S1 states of linear cata-condensed hydrocarbons due to the mode-selective internal conversion to the S0 state. This selectivity is likely to be seen in the S1 Φ(A) state of the D(2h) molecule.

Jet spectroscopy of buckybowl: electronic and vibrational structures in the S0 and S1 states of triphenylene and sumanene.

Sumanene is a typical buckybowl molecule with C3v symmetry. We observed a fluorescence excitation spectrum and a dispersed fluorescence spectrum of sumanene in a supersonic jet. Bowl effects were clarified by comparing the spectra with those of triphenylene (D3h symmetry), which is a planar prototype of nonplanar sumanene. The S1 (1)A1 ← S0 (1)A1 transition is symmetry allowed. We found the 0(0)(0) band in the fluorescence excitation spectrum at 357.78 nm; this band was missing in the forbidden S1 (1)A1(') ← S0 (1)A1(') transition of triphenylene. The transition moment was shown to be along the oblate symmetric top axis (out of plane) by the observed rotational contour. A large number of vibronic bands were observed, unlike in triphenylene. Some were considered to be out-of-plane vibrational modes, which lead to a bowl-to-bowl inversion reaction assisted by in-plane vibrations. We found that the vibronic bands were markedly weak in the high energy region of triphenylene-d12. This indicates that the fluorescence quantum yield is very low at the high vibrational levels in the S1 state due to the rapid radiationless transition. The main process is considered to be internal conversion to the S0 state. The nonplanar structural distortion may also enhance radiationless transitions. We could not, however, observe weakening of the vibronic bands in the fluorescence excitation spectrum of sumanene.

Electronic, vibrational, and rotational structures in the S0 1A1 and S1 1A1 states of phenanthrene.

Electronic and vibrational structures in the S(0) (1)A(1) and S(1) (1)A(1) states of jet-cooled phenanthrene-h(10) and phenanthrene-d(10) were analyzed by high-resolution spectroscopy using a tunable nanosecond pulsed laser. The normal vibrational energies and molecular structures were estimated by ab initio calculations with geometry optimization in order to carry out a normal-mode analysis of observed vibronic bands. The rotational structure was analyzed by ultrahigh-resolution spectroscopy using a continuous-wave single-mode laser. It has been demonstrated that the stable geometrical structure is markedly changed upon the S(1) ← S(0) electronic excitation. Nonradiative internal conversion in the S(1) state is expected to be enhanced by this structural change. The observed fluorescence lifetime has been found to be much shorter than the calculated radiative lifetime, indicating that the fluorescence quantum yield is low. The lifetime of phenanthrene-d(10) is longer than that of phenanthrene-h(10) (normal deuterium effect). This fact is in contrast with anthracene, which is a structural isomer of phenanthrene. The lifetime at the S(1) zero-vibrational level of anthracene-d(10) is much shorter than that of anthracene-h(10) (inverse deuterium effect). In phenanthrene, the lifetime becomes monotonically shorter as the vibrational energy increases for both isotopical molecules without marked vibrational dependence. The vibrational structure of the S(0) state is considered to be homogeneous and quasi-continuous (statistical limit) in the S(1) energy region.