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A study of neutral vanadium oxide clusters is conducted by photoionization time-of-light (TOF) mass spectroscopy, electronic spectroscopy, and density functional theory (DFT) calculations. Mass spectra of vanadium oxide clusters are observed by photoionization with lasers of three different wavelengths, namely, 18, 193, and 355 nm.

Research is done on infrared spectra of 2-hydroxypyridine (2HP) and its hydrogen-bonded clusters with water and methanol have been observed by IR-UV double-resonance spectroscopy. In conclusion, the cluster structures were examined using ab initio molecular orbital measurements.

Vibrational spectra of the methyl groups in CH3SH, CH3SCH3, CH3OH, and CH3OCH3 monomers were measured to analyze their complex features as a result of bend/umbrella‐stretch Fermi resonance. Multiple bands were recorded between 2800–3000 cm−1 associated with the vibrations of the methyl groups in CH3OH, and CH3OCH3. On the other hand, the corresponding spectra of CH3SH and CH3SCH3 are relatively simpler with main peaks between 2900 to 3000 cm−1. Theoretical ab initio anharmonic algorithm using six normal modes on a methyl group with potential energy surface at CCSD(T)‐F12/aug‐cc‐pVTZ quality is able to account for all the experimentally observed features across these four species. In CH3SCH3 and CH3SH, all three CH stretch fundamentals are above 2900 cm−1, but the fundamental of umbrella mode is lower than 1350 cm−1, thus only the overtone states of two bending modes are able to borrow sufficient intensities. In CH3OCH3 and CH3OH, umbrella modes have frequencies similar to the bending modes and the CH stretch fundamentals are red‐shifted to 2850–2950 cm−1 leading to more complex vibrational features due to better energy‐matching condition. [ABSTRACT FROM AUTHOR]

Infrared (IR) spectroscopy based on vacuum-ultraviolet one-photon ionization detection was carried out to investigate geometric structures of neutral and cationic clusters of acetic acid: (CH3COOH)2, CH3COOH–CH3OH, and CH3COOH–H2O. All the neutral clusters have cyclic-type intermolecular structures, in which acetic acid and solvent molecules act as both hydrogen donors and acceptors, and two hydrogen-bonds are formed. On the other hand, (CH3COOH)2+ and (CH3COOH–CH3OH)+ form proton-transferred structures, where the acetic acid moiety donates the proton to the counter molecule. (CH3COOH–H2O)+ has a non-proton-transferred structure, where CH3COOH+ and H2O are hydrogen-bonded. The origin of these structural differences among the cluster cations is discussed with the relative sizes of the proton affinities of the cluster components and the potential energy curves along the proton-transfer coordinate. [ABSTRACT FROM AUTHOR]

Infrared predissociation spectroscopy is carried out for the structure investigation of unprotonated cluster cations of protic molecules such as ammonia and methanol, which are generated through vacuum-ultraviolet one-photon ionization of their jet-cooled neutral clusters. The observed spectral features show that the cluster cations have the proton-transferred type structures, where a pair of a protonated cation and a neutral radical, NH4+...NH2 or CH3OH2+...OCH3, is formed. Theoretical calculations at the MP2 and B3LYP levels support the formation of the proton-transferred type structures for the cluster cations, and indicate that they are formed by proton-transfer following the photoionization of the neutral clusters. [ABSTRACT FROM AUTHOR]

Infrared predissociation spectroscopy of vacuum ultraviolet-pumped ion (IRPDS-VUV-PI) is performed on ammonia cluster cations (NH3)n+ (n=2–4) that are produced by VUV photoionization in supersonic jets. The structures of (NH3)2+ and (NH3)4+ are determined through the observation of infrared spectra and vibrational calculations based on ab initio calculations at the MP2/6-31G** and 6-31++G** levels. (NH3)2+ is found to be of the “hydrogen-transferred” form having the (H3N+–H...NH2) composition. In contrast, (NH3)4+ exhibits the “head-to-head” dimer cation (H3N...NH3)+ core structure, where the positive charge is shared between two ammonia molecules in the core, and two other molecules are hydrogen bonded onto the core. An unequivocal assignment of the infrared spectrum of (NH3)3+ has not been achieved, because the presence of two isomeric structures could be suggested by the observed spectrum and theoretical calculations. [ABSTRACT FROM AUTHOR]

The S[sub 1]-S[sub 0] electronic spectra, and the vibrational spectra of jet-cooled 2-pyridone (2PY) and its hydrogen bonded clusters, 2PY-H[sub 2]O and 2PY dimer, have been investigated by population labeling and various double-resonant vibrational spectroscopies. For bare 2PY, the S[sub 1]-S[sub 0] spectrum was measured by laser-induced fluorescence and population labeling spectroscopy. In addition, IR and Raman spectra of the NH stretching vibration were observed in S[sub 0] and S[sub 1]. The results led to the conclusion that 2PY has two close lying electronic states in the S[sub 1] region, whose structures are slightly different with respect to the NH group. It was also found that the NH stretching frequency becomes smaller in S[sub 1] than in S[sub 0], indicating that the NH bond strength of 2PY becomes weaker in S[sub 1]. The effect of the electronic excitation on the hydrogen bond strength has also been investigated by measuring the NH and OH stretching vibrations of the hydrogen bonded clusters in the two electronic states, and it was found that the hydrogen-bond strength is weaker in S[sub 1] than in S[sub 0]. For 2PY dimer, the IR and the Raman spectra of the NH stretching bands showed a clear intensity alternation, confirming its C[sub 2h] symmetric structure. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The vacuum-ultraviolet-ionization detected-infrared predissociation spectroscopy technique is employed to study the preparation of the neutral and cationic formamide-water clusters in a supersonic jet. These clusters are shown to exhibit a double ring type structure.

A study of gas-phase neutral titanium oxide clusters was conducted where both 118 nm single-photon ionization and 193 and 355 nm multiphoton ionization techniques were employed to detect the clusters. Mass spectra were measured as a function of oxygen content (0.1-6% O2/He) in the expansion/reaction gas used to generate the clusters.

Focuses on the vibrational spectroscopy of the key functional vibrations of 2-pyridone and its hydrogen-bonded clusters with water, methanol, dimethylether, as well as its dimer, using infrared-ultraviolet and stimulated Raman-UV double resonance methods. Appropriateness of the ring-type hydrogen-bonded structure for the cluster with water or methanol.