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Laser-induced fluorescence (LIF) spectroscopy and fluorescence-detected ultraviolet (UV)-UV and infrared (IR)-UV double-resonance spectroscopy are used to study the structure of jet-cooled L-tyrosine (L-Tyr). The comparison of the results of L-Tyr and L-phenylalanine have shown that conformers of L-Tyr existing under jet-cooled condition have side-chain conformers similar to conformers B, D, E, and X of L-phenylalanine.

The study observes NH stretching vibrations of jet-cooled aniline and its various derivatives in the neutral and cationic ground states. The results reveal that the intramolecular hydrogen bond formation was found for o-cyanoaniline in both the neutral and cationic ground states based on the infrared spectra of deuterated isotopomers resulting in hydrogen bond strength, which is remarkably enhanced upon ionization.

Vibrational spectra of the CH stretching vibration of diazine molecules, pyrimidine and pyrazine, were measured by infrared (IR)–vacuum ultraviolet (VUV) spectroscopy under the jet‐cooled gas‐phase condition. The observed IR spectra were analyzed by three anharmonic algorithms to account for the Fermi‐resonance (F‐R). The anharmonic analysis of the F‐R pattern was performed with second‐order vibrational perturbation theory (VPT2) with quartic potentials (QPs) at the DFT level of B2PLYP/6–311++G(d,p), followed by vibrational configuration interaction (VCI) method with the same QP. The VPT2 + QP method reasonably reproduced most of the bands in the observed spectra for all the species, especially for pyrimidine, a decent agreement is obtained with respect to the band positions and relative intensities. The analyses of the spectra show that all the observed spectra can be well interpreted by the F‐R between the CH stretching fundamentals and the first overtone and 1 + 1 combination bands involving the in‐plane CH bending vibrations and the contribution of the higher‐order anharmonic coupling to the observed spectra seems to lead to red‐shift of the F‐R patterns. Discrete variable representation based methods with potential energy surfaces at CCSD/aug‐cc‐pVDZ theory with 10 degrees of freedom were also carried out to assess the quality of QP at DFT level. [ABSTRACT FROM AUTHOR]

Infrared photodissociation spectra of n-propylbenzene (n-PB)-Ar cluster cations are presented in the CH stretching vibrational region. Spectral analysis suggests that ionization of (n-PB)-Ar cluster cations show delocalization of positive charge of aromatic ring into the alkyl chain.

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.

Research was done on the vibrational relaxation of the OH/OD stretching mode of phenol and its cluster with Ar or H2O which had been examined directly by nanosecond IR--UV pump--probe spectroscopy. In conclusion, the experiment on the phenol--Ar and phenol--H2O reveal the OH stretching level, which showed a fast single exponential decay curve, indicating a transformation from intermediate coupling to the statistical limit upon the cluster formation.

Infrared-ultraviolet double-resonance spectroscopic method was applied to the conformational investigation of rotamers of aryl alcohol. The objective was to produce and discriminate various structures of aryl alcohol homologues by putting stress on the OH stretching vibration which untangles the structural ambiguity and provides information regarding the acidity of different structures. Results suggest that different OH stretching frequencies are associated with different rotamers and that the ability of intramolecular hydrogen bonding with the benzene pi-electron decreases with an increase in alkyl chain length.

Methyl salicylate (MS) and its hydrogen-bonded clusters with several solvents in the OH stretch region are studied using infrared spectroscopy. Results show that each cluster holds the intramolecular hydrogen bond although the bond is perturbed by the intermolecular hydrogen-bond formation with the solvent molecules. Intramolecular bond breakdown with microsolvation was not observed in small size MS clusters while complete tranformation from intra- to intermolecular hydrogen was found in tropolone.

Supersonic jet spectroscopic method is used in the isolation of the most stable conformer of 2-phenylpropanal. The jet conditions enable only one conformer of 2-phenylpropanal to exist. The conformer exhibits two bands having red shifts of 65 and 32 per centimeter.

S-cis conformation is the major orientation in the addition reaction of alpha,beta-unsaturated esters with metal amides. Supersonic jet spectroscopic analysis of methyl cinnamate reveals equal populations of s-cis and s-trans conformers at room temperature. NOE experiments of methyl cinnamate reveal the dominance of the s-cis form in solution at low temperature. X-ray analyses of enoates reveal the preference of the s-cis form in the solid state.