Slow-electron velocity-map imaging study of aniline via resonance-enhanced two-photon ionization method

Zehua Qu; Zhengbo Qin; Xianfeng Zheng; Hui Wang; Guanxin Yao; Xianyi Zhang; Zhifeng Cui

doi:10.1016/j.saa.2016.09.046

Slow-electron velocity-map imaging study of aniline via resonance-enhanced two-photon ionization method

Spectrochim Acta A Mol Biomol Spectrosc. 2017 Feb 15:173:432-438. doi: 10.1016/j.saa.2016.09.046. Epub 2016 Sep 28.

Authors

Zehua Qu¹, Zhengbo Qin², Xianfeng Zheng³, Hui Wang¹, Guanxin Yao¹, Xianyi Zhang¹, Zhifeng Cui¹

Affiliations

¹ Institute of Atomic and Molecular Physics, Anhui Normal University, Wuhu, Anhui 241000, China.
² Institute of Atomic and Molecular Physics, Anhui Normal University, Wuhu, Anhui 241000, China. Electronic address: asiake04@mail.ahnu.edu.cn.
³ Institute of Atomic and Molecular Physics, Anhui Normal University, Wuhu, Anhui 241000, China. Electronic address: xfzheng@mail.ahnu.edu.cn.

PMID: 27705848
DOI: 10.1016/j.saa.2016.09.046

Abstract

Slow electron velocity-map imaging (SEVI) of aniline has been investigated via two-color resonant-enhanced two-photo (1+1') ionization (2C-R2PI) method. A number of vibrational frequencies in the first excited state of neutral (S₁) and ²B₁ ground electronic state of cation (D₀) have been accurately determined. In addition, photoelectron angular distributions (PADs) in the two-step transitions are presented and reveal a near threshold shape resonance in the ionization of aniline. The SEVI spectra taken via various S₁ intermediate states provide the detailed vibrational structures of D₀ state and directly deduce the accurate adiabatic ionization potential (IP) of 62,271±6cm^-1. Ab initio calculations excellently reproduce the experimental IP value (Theo. 62,242cm^-1). For most vibrational modes, good agreement between theoretical and experimental frequencies in the S₀ and D₀ states of aniline is obtained to aid us to clearly assign vibrational modes. Especially, the vibrational frequencies calculated at the CASSCF level are much better consistent with experimental data than that obtained using the TDDFT and CIS methods.

Keywords: Aniline; Resonance-enhanced multiphoton ionization (REMPI); Time-of-flight; Velocity-map imaging.