Sub‐Doppler Zeeman Spectroscopy of the CS₂ Molecule

Abstract

The Zeeman splitting of rotational lines in the V system of CS2 were systematically studied, using a cw single mode frequency doubled dye laser with linear and circular polarization in a cold collimated molecular beam within a tunable magnetic field up to 0.2 Tesla. Two sources of magnetic moments of levels in the excited 1B2 state could be identified. First, a second order spin‐orbit spin‐rotational coupling to the spin components of the 3A2(3Δu) electronic state is responsible for the generated magnetic moments in the rotational levels of the 1B2 state, which seem to be irregularly behaved. Because of the insufficient information about the spin components of the triplet state 3A2(3Δu) we developed a model of two interacting levels, which can explain many of the observed patterns of the rotational levels in a magnetic field. Secondly, an electronic Coriolis coupling (Renner‐Teller coupling) betwen the two Born‐Oppenheimer component states 1A2(1Δu) and 1B2(1Δu) leads to a partly quenched electronic orbital angular momentum. Consequently, the Landé gJ factors posses a {J(J+1)}−1 dependence. This has been observed for the π bands of the 1B2(1Δu) state. Moreover, the analysis of the measured Zeeman patterns yields valuable information about the coupling parameters.

Effects of magnetic field on the 15V 31 344.9 band of CS2 studied by sub-Doppler high-resolution spectroscopy

“…This was first observed by Habib et al 10 Our spectrum is, however, superior in both sensitivity and resolution, which allows the unambiguous assignment of M . This assignment and accordingly the interpretation of the Zeeman pattern differs from that proposed by Habib et al 11 as will be shown below.…”

“…If the energy of the perturbed level 1 B 2 (vЈ;03M ) * is close to that of ͉ 3 A 2 (A 1 ϩB 1 )v 0 ;13M ͘ ͑this is the case proposed by Habib et al 11 ͒, the Zeeman interaction between the mixed level 1 B 2 (vЈ;03M ) * and ͉ 3 A 2 (A 1 ϩB 1 )v 0 ;13M ͘ is zero for M ϭ0 as can be seen from the formula S in Eq. ͑20͒.…”

“…We measured more extensively with higher resolution and sensitivity. Our experimental results show that this new transition cannot be explained by the mechanism proposed by Habib et al 11 We shall report the experimental results and their interpretation in this article. The reason why large Zeeman splittings are observed for many lines of the V system will be revealed in this study.…”

“…High-resolution spectroscopy was first applied to study the magnetic field effect on the 1 B 1 state of pyrimidine. 7 Recently, Zeeman spectra of the V system of CS 2 were measured parallel and independently by Katô et al 8,9 and by Habib et al 10,11 Habib et al found a new transition to appear close to the P͑4͒ line, and they identified the rotational quantum number of the upper level to be JЈϭ3. We also independently observed the same phenomena.…”