Structures and Anharmonic Analyses of the O-H Stretching Vibrations of Jet-Cooled Benzoic Acid (BA), (BA)(HO), and (BA)(HO) ( = 1, 2) Clusters, and Their Ring-Deuterated Isotopologues Measured with IR-VUV Spectroscopy─Unraveling the Complex Anharmonic Couplings in the Cyclic Structures.

The IR spectra of benzoic acid (BA), (BA)(HO) and (BA)(HO) ( = 1, 2) clusters, and their ring-deuterated isotopologues in the 2800-3750 cm region were measured with IR-vacuum ultraviolet spectroscopy under the jet-cooled condition. For (BA)(HO) and (BA)(HO), only a single isomer was observed for each species, whereas for (BA)(HO) and (BA)(HO), more than one isomers were present. The observed IR spectra were very complex and showed similar structures between (BA)(HO) and their ring-deuterated isotopologues (BA-)(HO) for specific values of and .

Structures of (Pyrazine) and (Pyrazine)(Benzene) Dimers Investigated with Infrared-Vacuum Ultraviolet Spectroscopy and Quantum-Chemical Calculations: Competition among π-π, CH···π, and CH···N Interactions.

The structures of a pyrazine dimer (pyrazine) and (pyrazine)(benzene) hetero-dimer cooled in a supersonic beam were investigated by the measurement of the infrared spectra in the C-H stretching region with infrared-vacuum ultraviolet (IR-VUV) spectroscopy and quantum-chemical calculations. The stabilization energy calculation at the CCSD(T)/aug-cc-pVTZ level of theory predicted three isomers for (pyrazine) and three for (pyrazine)(benzene) with energy within 6 kJ/mol. Among them, the cross-displaced π-π stacked structure is the most stable in both dimers.

Structures of Pyridine-Water Clusters Studied with Infrared-Vacuum Ultraviolet Spectroscopy.

The infrared (IR) spectra of the O-H stretching vibrations of pyridine-water clusters (Pyd)(HO), with , = 1-4, have been investigated with infrared-vacuum ultraviolet (VUV) spectroscopy under a jet-cooled condition. The time-of-flight mass spectrum of (Pyd)(HO) by VUV ionization at ∼9 eV showed an unusual intensity pattern with very weak ion signals for = 1 and 2 and stronger signals for ≥ 3. This unusual mass pattern was explained by a drastic structural change of (Pyd)(HO) upon the VUV ionization, which was followed by the elimination of water molecules.

Vacuum Ultraviolet Photoionization Induced Proton Migration and Formation of a New C-N Bond in Pyridine Clusters Revealed by Infrared Spectroscopy and Mass Spectrometry.

The structures and reactions of pyridine (Pyd) cluster cations in a supersonic molecular beam generated upon photoionization at 9.2-9.4 eV were investigated by infrared (IR) action spectroscopy.

IR-VUV spectroscopy of pyridine dimers, trimers and pyridine-ammonia complexes in a supersonic jet.

The infrared spectra of the C-H stretching vibrations of (pyridine)m, m = 1-3, and the N-H stretching vibrations of (pyridine)m-(NH3)n, m = 1, 2; n = 1-4, complexes were investigated by infrared (IR)-vacuum ultraviolet (VUV) spectroscopy under jet-cooled conditions. The ionization potential (IP0) of the pyridine monomer was determined to be 74 546 cm-1 (9.242 eV), while its complexes showed only smooth curves of the ionization thresholds at ∼9 eV, indicating large structural changes in the ionic form.