Sub-Doppler laser spectroscopy of the 1<i>B</i>2(1Δ<i>u</i>) state of CS2 in a cold molecular beam

Abstract

Sub-Doppler excitation spectra of CS2 in the spectral range 30200−32300 cm−1 have been extensively measured with a frequency-doubled single mode cw dye laser in a cold collimated argon beam, seeded with CS2. From the rotational analysis of the measured spectra, the geometry and the position of the barrier to linearity of the CS2 molecule in the excited 1B2(1Δu) state has been determined. The observed bands are heavily perturbed and cluster around some intense vibrational transitions. A statistical analysis of the distribution of these bands showed that no chaotic behavior is present in the considered energy region and therefore a non-linear interaction with highly excited vibrational levels of the ground state cannot be responsible for this irregular vibronic structure, although chaotic regions for vibrational energies E≳12000 cm−1 in the electronic ground state have been reported in the literature. Different coupling mechanisms causing the observed perturbations of the rotational and vibrational structure are also discussed.