物理化学学报 >> 2009, Vol. 25 >> Issue (12): 2488-2492.doi: 10.3866/PKU.WHXB20091206

研究论文 上一篇    下一篇

1-萘酚的紫外共振双光子电离光谱

张树东, 张海芳, 曾文碧   

  1. 山东省激光偏光与信息技术重点实验室, 曲阜师范大学物理系, 山东 曲阜 273165; 台湾中央研究院, 原子与分子科学研究所, 台湾 台北 106
  • 收稿日期:2009-07-13 修回日期:2009-08-21 发布日期:2009-11-27
  • 通讯作者: 张树东 E-mail:zhangsd2@126.com

UV Resonant Two-Photon Ionization Spectrum of 1-Naphthol

ZHANG Shu-Dong, ZHANG Hai-Fang, TZENG Wen-Bi   

  1. Shandong Provincial Key Laboratory of Laser Polarization and Information Technology, Department of Physics, Qufu Normal University, Qufu 273165, Shandong Province, P. R. China; Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 106, Taiwan, P. R. China
  • Received:2009-07-13 Revised:2009-08-21 Published:2009-11-27
  • Contact: ZHANG Shu-Dong E-mail:zhangsd2@126.com

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摘要：

利用脉冲分子束技术, 在305-322 nm范围内研究了1-萘酚(1NP)的共振双光子电离(R2PI)光谱. 1NP分子存在cis和trans两种旋转异构体, 但实验中仅观测到trans异构体的电子振动跃迁光谱, 其S1←S0跃迁的(0-0)带头出现在317.90 nm(即31456 cm-1)位置. 利用光谱选律及ab initio和密度泛函(DFT)计算, 对trans异构体在S1态的振动模进行标识, 得出主要对应于对称性为a'的平面内振动模. 计算显示, cis异构体在电子基态S0的能量较trans异构体高出439 cm-1, 而第一激发能却比trans异构体的低1216 cm-1, 与之相应的实验值分别是220和274 cm-1. 计算数值与实验结果在能量变化趋势上完全一致. 共振双光子电离谱中没有观测到cis异构体的光谱信号, 其原因可归结为分子束的有效冷却效应使得处于基态的cis异构体的布居数密度相对trans异构体极低, 导致cis光谱信号太小而未能被探测到.

关键词: 电子激发态, 1-萘酚, 共振双光子电离, Ab initio计算

Abstract:

The resonant two-photon ionization (R2PI) spectrum of 1-naphthol (1NP) was studied from 305 to 322 nm using supersonic molecular beam technique. 1NP has two rotamers: cis and trans. The R2PI spectrum was used to characterize the S1←S0 transition of the trans species and its original band appeared at 317.8 nm (31456 cm-1). The vibrational bands of the trans species from the R2PI spectrum can be assigned to in-plane vibrational modes with a' symmetry. Ab initio and density functional theory (DFT) calculations indicate that the cis rotamer has higher energy than the trans rotamer by 439 cm-1 in the ground state but it has a lower exciting energy than the trans rotamer by 1216 cm-1 for the S1←S0 transition. These calculated results are in good agreement with the experimental trend where the difference between the cis and trans energies in the S0 state is 220 cm-1 and the difference between the cis and trans exciting energies is 274 cm-1. There are no spectral features from the cis rotamer in the R2PI spectrum and we attribute this to the efficient cooling conditions in the molecular beam, which leads to a very small cis rotamer population with the higher energy (220 cm-1).

Key words: Electronic excited state, 1-Naphthol, Resonant two-photon ionization, Ab initio calculation