Development of multidimensional mass spectrometry combined with laser photodissociation spectroscopy

我们开发了一种新的光谱测量设备，用于尺寸选择的分子团簇离子以及分子碎片离子的光谱测量。该装置包括超声分子束源和电离段，用于尺寸选择的Q极质量滤光器，与激光光解相结合的离子陷阱池，以及带有离子探测器的第二Q极质量分析器。利用这一装置，可以对阳离子的电子跃迁和振动跃迁进行光谱测量。本项目现阶段的主要结果如下：1.发展了一种新的喷冷分子阳离子红外光谱技术。该方法包括通过神经激发态激发高里德堡态的双色激光，用红外光对其离子核进行振动激发，以及离子核的振动自电离。(1)观察取代苯酚阳离子的OH伸缩振动，研究离子状态下的分子内氢键；(2)观察芳烃阳离子的CH伸缩振动，用常规方法研究其不可及的振动能级。本文建立了分子团簇的IR-UV双共振谱，并结合量子力学从头算方法研究了它们的分子间结合结构：(1)2-吡啶酮及其团簇的振动光谱和团簇结构；(2)苯甲腈团簇与不同分子的结构和振动弛豫；(3)苯甲醇旋转体及其水溶剂化团簇的结构研究。

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.