Development of multidimensional mass spectrometry combined with laser photodissociation spectroscopy

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We have developed a new equipment for spectroscopic measurements of size-selected molecular cluster ions, as well as molecular fragment ions. The setup consists of a supersonic molecular beam source, and ionization section, a Q-pole mass filter for size-selection, an ion trap cell combined with laser photodissociation section, and a second Q-pole mass analyzer with a ion detector. With this setup, spectroscopic measurements for electronic and vibrational transitions of cations can be performed.Major results at the present stage of the project are the following :1. A new infrared (IR) spectroscopic technique for jet-cooled molecular cations is developed. The method involves two-color laser excitation via neural excited state to high Rydberg states, vibrational excitation of its ion core with IR light, and vibrational autoionization of the ion core. It has been applied for the several compounds ;(1) Observation of OH stretching vibrations of substituted phenol cations to investigate intramolecular hydrogen bonds in ionic states.(2) Observation of CH stretching vibrations of aromatic hydrocarbon cations to study the inaccessible vibrational levels with conventional methods.2. IR-UV double resonance spectroscopy of size-selected molecular clusters is established for the investigation of their intermolecular binding structures in combination with ab initio quantum mechanical calculations.(1) Vibrational spectroscopy and cluster structures of 2-pyridone and its clusters.(2) Structure and vibrational relaxation of benzonitril clusters with various molecules.(3) Structural investigations of benzyl alcohol rotomers and of its water solvated clusters.