高強度・短パルスレーザー照射によるエタノール分子の解離性イオン化における円偏光と直線偏光の違い

Polarization dependence of dissociative ionization of ethanol by intense laser irradiation

赤木 浩; 乙部 智仁; 板倉 隆二; 穂坂 綱一*; 山内 薫; 横山 淳

Akagi, Hiroshi; Otobe, Tomohito; Itakura, Ryuji; Hosaka, Koichi*; Yamanouchi, Kaoru; Yokoyama, Atsushi

高強度・短パルスレーザー照射によって進行するエタノールの解離性イオン化過程について、光電子とイオンの同時計測実験を行った。円偏光の場合、同じレーザー強度の直線偏光より解離イオンの生成量が少なくなる傾向がある。また、1114TW/cmのレーザー強度において、円偏光の場合と直線偏光の場合ではC-C結合切断と相関する光電子スペクトルが劇的に変化することを明らかにした。時間依存密度汎関数法による数値計算と比較し、解離に至るイオン化ダイナミクスについて議論する。

In the present work, ethanol molecules are irradiated with a circularly-polarized intense laser field (I = 1.4 10 W/cm), and the produced electron and ion are measured in coincidence. The channel-specific photoelectron spectra correlated with the C-C and C-O dissociation channels are similar to that correlated with the parent ion, showing the series of distinctive ATI peaks. These are the signature representing that the electronic ground state of parent ions is initially prepared upon the ionization, and then, the subsequent electronic excitation leading to the C-C or C-O dissociation takes place within the same laser pulse. For the linear polarization with similar laser field intensity (1.7 10 W/cm), the ATI series is also observed, but less pronounced. This means that the electronic excitation of the parent ion is more efficiently induced in the circularly polarized laser field than in the linearly polarized one.