Rotationally resolved laser-induced fluorescence and zeeman quantum beat spectroscopy of the V1B2state of jet-cooled CS2

  • Ochi N
  • Watanabe H
  • Tsuchiya S
 et al. 
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Abstract

The rotationally resolved laser-induced fluorescence (LIF) excitation spectrum of V system bands (V1B2≈X1Σ1gtransition) of CS2cooled in a supersonic jet has been observed. In a supersonic jet of CS2/Ar or He mixture, the rotational temperature of CS2is reduced to less than 10 K, and thus the LIF excitation spectrum is simplified significantly. Two types of rotational structure are found; one is composed of P and R branch transitions from even J″ levels and the other is of P, Q, and R branch transitions from even as well as J″. The bands with the former rotational structure are assigned to transitions to K′ = O levels of1B2state, the bands with the latter structure to transitions to K′ = 1 levels from the (O, 11, O) level of the electronic ground state, i.e. vibrationally hot bands. This assignment is supported by the further evidence that these hot bands disappear when the supersonic jet includes a third-body gas such as NH3which enhances the vibrational relaxation of CS2. Calculation of transition moments for respective leads to the conclusion that the upper levels of the V system bands are located in the region close to or higher than the potential barrier of the bending vibration of excited CS2. The radiative lifetime of CS2in single rovibronic levels of the1B2state is in the range of 2-8 μs which is of the same order of magnitude as that calculated from the absorption coefficient. It tends to be longer for higher J levels or for higher vibronic levels. Zeeman quantum beating is observed in the fluorescence decay of excited CS2for a number of rovibronic levels under a weak magnetic field, and thus a magnetic moment associated with each rovibronic level can be determined. The g values are around 0.02 and tend to be smaller in higher J levels for some vibronic states. Based on the the observed radiative lifetime and the g value, it is suggested that the1B2state is perturbed by a spin-rotation interaction with two spin components, A1and B1of the3A2orbital state besides a strong spin-orbit coupling with the R3B2state. © 1987.

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Authors

  • Nobuaki Ochi

  • Hajime Watanabe

  • Soji Tsuchiya

  • Seiichiro Koda

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