激发到电子C态和D态的水分子的超快预解离动力学

Ultrafast predissociation dynamics of water molecules excited to the electronic C and D states.

作者信息

Steinkellner O, Noack F, Ritze H-H, Radloff W, Hertel I V

机构信息

Max-Born-Institut für Nichtlineare Optik und Kurzzeitspektroskopie, Max-Born-Strasse 2a, 12489 Berlin, Germany.

出版信息

J Chem Phys. 2004 Jul 22;121(4):1765-70. doi: 10.1063/1.1760732.

DOI:10.1063/1.1760732

PMID:15260726

Abstract

Two-photon excitation with femtosecond laser pulses in the spectral range 240-250 nm was used to prepare vapor phase H(2)O and D(2)O in the C (1)B(1) and D (1)A(1) states. Both states are predissociated via the B (1)A(1) state, forming excited OH/OD(A (2)Sigma(+)) as well as ground state OH/OD(X (2)Pi). We used ultrashort infrared probe pulses (1.65-2.42 microm) to control the ratio between these excited and ground state fragments originating from the dissociation process. Time resolved detection of the OH/OD(A (2)Sigma(+)) --> OH/OD(X (2)Pi) fluorescence allows us to monitor the dynamics of the predissociation. For the heterogeneous predissociation out of the C(1)B(1) state life times of (0.5 +/- 0.1) ps and (1.2 +/- 0.1) ps were found for H(2)O and D(2)O, respectively. The purely homogeneous character of the predissociation out of the D (1)A(1) state was monitored.

摘要

利用光谱范围为240 - 250 nm的飞秒激光脉冲进行双光子激发，制备处于C (1)B(1)和D (1)A(1)态的气相H₂O和D₂O。这两个态都通过B (1)A(1)态预解离，形成激发态的OH/OD(A (2)Σ⁺)以及基态的OH/OD(X (2)Π)。我们使用超短红外探测脉冲（1.65 - 2.42微米）来控制源自解离过程的这些激发态和基态碎片之间的比例。对OH/OD(A (2)Σ⁺) → OH/OD(X (2)Π)荧光进行时间分辨检测，使我们能够监测预解离的动力学过程。对于从C(1)B(1)态发生的非均匀预解离，发现H₂O和D₂O的寿命分别为(0.5 ± 0.1) ps和(1.2 ± 0.1) ps。监测了从D (1)A(1)态发生的纯均匀预解离特性。