若手のショートレビュー

希ガスダイマーイオンの振動準位と解離過程

Vibrational Levels and Dissociation Processes of Rare Gas Dimer Ions

吉井　裕
Hiroshi YOSHII

希ガスダイマーは，希ガス原子同士が弱いファンデルワールス力のみのよって結びついたものである．我々は，しきい光電子分光法による希ガスダイマーイオンの研究をすすめてきた．本レビューでは，しきい光電子分光法により観測されたAr₂⁺ の振動準位と，しきい光電子−光イオン−コインシデンス法によって観測された，KrXe⁺ の振動準位について解説する．さらに，Kr₂⁺ の解離過程について，詳細な解析を行なった結果も報告する．

Synopsis:Threshold photoelectron spectroscopy is a useful tool for measuring vibrational levels of rare gas dimer ions. In this short review, features of threshold photoelectron spectroscopy are introduced. After that, the observed vibrational levels of Ar₂⁺ are described in detail. Explanations for the vibrational levels of KrXe⁺ measured by threshold photoelectron-photoion coincidence technique are also given. In the subsequent study, it is revealed that the II(1/2u) states of Kr₂⁺ and Xe₂⁺ completely dissociate via optical transitions to the repulsive I(1/2g) states, while that of Ar₂⁺ does not dissociate. Precise analysis of the time-of-flight spectrum for the Kr⁺ fragment from the Kr₂⁺ II(1/2u) state is also shown. The potential energy curve of the I(1/2g) state and the lifetime of the optical transition from the II(1/2u) state to the I(1/2g) state are obtained from this analysis.

Keywords:Threshold photoelectron spectroscopy, rare gas dimmer, coincidence, dissociation