DOPPLER-FREE TWO-PHOTON ABSORPTION SPECTROSCOPY AND THE ZEEMAN EFFECT OF BENZENE
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Date
2002
Journal Title
Journal ISSN
Volume Title
Publisher
Ohio State University
Abstract
A Doppler-free absorption spectrum and the Zeeman effect of the $A^{1}B_{2u} \leftarrow X^{1}A_{1g}$ transition of benzene have been measured by means of two-photon absorption spectroscopy within an external cavity. Rotational lines were fully resolved and the accurate molecular constants have been determined for the $A^{1} B_{2u} (v_{14} = 1, v_{1} = 1)$ state. The Zeeman splittings for lines of a given J were observed to increase regularly with K and reach a maximum at $K = J$. This demonstrates that the magnetic moment lies along the c axis (perpendicular to the molecular plane). The magnetic moment of the $A^{1} B_{2u} (u_{14} = 1, v_{1} = 1, J = 43, K = 43)$ level was determined to be $0.005 \mu_{B}$. The Zeeman splittings of the $K = J$ levels were observed to increase with increasing J. It is concluded that the $S_{1}{^{1} B_{2u}}$ state is mixed with the $^{3}E_{2u} (\sigma,\pi^{\ast} or \sigma^{\ast},\pi)$ state. The $^{1}B_{2u}(S_{1}) \rightarrow {^{3}}B_{1u}(T_{1})$ and $^{1}B_{2u}(S_{1}) \rightarrow {^{3}}E_{1u}(T_{2})$ intersystem crossings are suggested to occur through the vibronic interactions between $^{3}E_{2u}$ and $^{3}B_{1u}(T_{1})$ and between $^{3}E_{2u}$ and $^{3}E_{1u}(T_{2})$ through the mixed $^{3}E_{2u}$ component, respectively, and the spin-orbit interaction between the the $S_{1}{^{1} B_{2u}}$ and $^{3}E_{2u} (\sigma,\pi^{\ast} or \sigma^{\ast}\pi)$ $states.^{a}$
Description
$^{a}$M. Misono, J. G. Wang, M. Ushino, M. Okubo, H. Kat\^{o}, M. Baba, and S. Nagakura, J. Chem. Phys., 116, 162 (2002).
Author Institution: Faculty of Integrated Human Studies, Kyoto University; Molecular Photoscience Research Center, Kobe University
Author Institution: Faculty of Integrated Human Studies, Kyoto University; Molecular Photoscience Research Center, Kobe University