Development of ionization detected infrared spectroscopy and its application to overtone spectroscopy of molecules and clusters

本文提出了一种新的红外光谱法，即非共振电离检测红外光谱法（简称，NID-IR）是一种IR-UV双共振光谱法，其通过由UV激光引起的选择性电离来检测振动激发的分子。由于电离检测，由于直接吸收，与传统的IR光谱相比，NID-IR光谱具有非常高的灵敏度。红外光谱已应用于苯酚、萘酚和笼状胺等分子，在超音速射流条件下观察到了这些分子的红外跃迁，特别是，在2400 ~ 14000 cm ~（-1）范围内成功地观察到了喷冷苯酚的红外跃迁。1.由于OH伸缩振动的第一至第四量子、CH泛频以及各种组合振动的存在，光谱显示出清晰的振动结构，测量了OH伸缩模的离解能，发现OH泛音的带宽随振动量子数的增加而减小，并与慢弛豫时的带形进行了比较，结果表明，分子内振动重分布（IVR）引起的谱带展宽是决定其谱带形状的主要因素，氘对能带形状的影响表明苯酚IVR中存在门道态.

A new IR spectroscopy has been developed.This spectroscopy named nonresonant ionization detected IR spectroscopy (shortly, NID-IR) is a kind of IR- UV double resonance spectroscopy which detects a vibrationally excited molecule by selective ionization due to a UV laser.Because of the ionization detection, NID-IR spectroscopy has very high sensitivity in comparison to the traditional IR spectroscopy due to direct absorption.The NID-IR spectroscopy has been applied to various molecules such as phenol, naphthol and caged amine.The IR transition of these molecule has observed in a supersonic jet condition.In special, IR transition of jet cooled phenol has successfully been observed from 2400 cm-1 to 14000 cm-1.The spectrum shows clear vibrational structures due to the first to the forth quantum of the OH stretching, CH overtones and various combination vibrations.The vibrational frequency, auharmonicity, and the dissociation energy of the OH stretching mode has been measured.It is found that the band width of OH overtones has been decreasing with increase in vibrational quantum number.From the comparison to the calculated band shape assuming slow relaxation, it is concluded that the band shape is mainly determined by the broadening due to the intramolecular vibrational redistribution (IVR).The existence of a doorway state in IVR of phenol has been suggested from the deuterium effect on the band shape.