Doppler-free two-photon absorption spectroscopy and the Zeeman effect of the A 1B2u←X 1A1g14111 band of benzene

Abstract

A Doppler-free absorption spectrum and the Zeeman effect of the A 1B2u(v14=1,v1=1)←X 1A1g(v=0) transition of benzene have been measured by means of two-photon absorption spectroscopy with counterpropagating light beams of identical wavelength within an external cavity. Rotational lines were fully resolved, and 647 QQ lines of J=0–43, K=0–43 have been assigned. The molecular constants of the A 1B2u(v14=1,v1=1) state have been determined as A=B=0.181 046 1, C=0.090 548 9, DJ=0.544×10−7, DJK=−1.093×10−7, DK=0.587×10−7, and T0=40 578.2672 cm−1. 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 1B2u(v14=1,v1=1,J=43,K=43) level was determined to be 0.005μB. The Zeeman splittings of the K=J levels were observed to increase with increasing J. Via analysis of the rotationally resolved Zeeman spectra, it is concluded that the A 1B2u state is mixed with the E2u3 state. This new finding suggests that vibronic interactions between E2u3 and B1u3(T1) and between E2u3 and E1u3(T2) through the mixed E2u3 component, contribute to the B2u1(S1)→3B1u(T1) and B2u1(S1)→3E1u(T2) intersystem crossings, respectively.

Spectroscopic study on deuterated benzenes. III. Vibronic structure and dynamics in the S1 state

“…It was shown by ultrahigh-resolution laser spectroscopy that intersystem crossing (ISC) to the triplet state is not effective even at low vibronic levels. 26,29,30 In particular, channel three is considered to be a combined process of the IVR and IC. By the rotational analysis of 6 1 1 3 and 14 1 1 2 levels of C 6 H 6 , the IC rate was found to be strongly dependent on the rotational quantum numbers, while the anharmonic Coriolis interaction dominates the IVR process.…”

High resolution molecular spectroscopy assisted by an optical frequency comb

“…High resolution molecular spectroscopy is of great interest not only to fundamental science but to various applications [1,2]. Since the most molecular spectra have the complex features distributed over a wide frequency range, a desirable spectroscopic system should satisfy the requirements for high resolution and wide tunability.…”

Precise frequency measurement and characterization of a continuous scanning single-mode laser with an optical frequency comb

“…High-resolution spectroscopy is a powerful tool for observing minute effects in the spectra. Moreover, detailed structures and dynamics in the excited states of polyatomic molecules such as benzene [1], naphthalene [2], and dihydrophenanthrene [3] have been studied by Doppler-free spectroscopies [4]. In high-resolution molecular spectroscopy, singlemode cw lasers have been commonly used because of their narrow line widths.…”

“…For calibrating the laser frequency, stabilized etalons have been conventionally employed in high-resolution spectroscopies [1][2][3]. However, the accuracy of the scheme is limited to a few megahertz due to frequency dispersions and passlength fluctuations of the etalons.…”

“…Because the fluctuation of f n is sufficiently small, the fluctuation of f beat contains the information on the scanning laser fluctuation, as shown in Eq. (1). Therefore, we can analyze the characteristics of the scanning laser according to the beat frequency distribution.…”