Sub-Doppler excitation spectra of CS2 in the spectral range of 29 600–32 800 cm−1 (V-system) are measured with a frequency doubled continuous wave (cw) single-mode dye laser. The ultraviolet (UV) radiation is generated in an external enhancement cavity. The average output power is about 5 mW, which is sufficient to resolve weak rotational lines in the excitation spectra of hot bands from the (0,22,0) level of the ground state. This increased the number of measured transitions with K>0 considerably. The low temperature achieved by adiabatic cooling of CS2 seeded in a supersonic argon beam simplifies the spectrum and allows an exact assignment of the rotational lines. Based on new ab initio calculations, a revised electronic state and vibrational assignment of the bands were necessary and will be presented. From this vibrational analysis the geometry, the position of the barrier to linearity, and the rotational constants of the CS2 molecule in the V 1B2(1Δu) state have been determined, revising former results. A statistical analysis of the positions of all measured bands shows a pure Poissonian nearest level distribution indicating no correlation between neighboring vibrational levels nor long-range interactions.
Single rovibronic levels in the perturbed B21(Δu1) state of CS2 molecules in a cold molecular beam were excited by ultraviolet (UV) photons from a frequency doubled single mode continuous wave (cw) dye laser. The dispersed fluorescence spectrum, detected by a liquid nitrogen (LN) cooled charge coupled device (CCD) array behind a monochromator allowed the determination of vibrational term values in the X(1Σg+) state from the (0,00,0) level up to 20 000 cm−1. Based on calculations including Fermi resonances, most of the measured vibrational bands could be assigned to several vibronic ground state level progressions. A statistical analysis of the positions of all measured levels shows for the nearest neighbor distances and the Δ3 statistics a pure Poissonian distribution. This indicates that no strong correlation between neighboring vibrational levels nor long range interactions are present and therefore no chaotic behavior could be found in contrast to the cases of NO2 and SO2.
Direct observation of the (2) 3Π u state of Cs2 by resonance enhanced two photon ionization spectroscopy in a very cold molecular beam J. Chem. Phys. 99, 5677 (1993); 10.1063/1.465936 Dopplerfree high resolution laser spectroscopy of the Cs2 D 1Σ+ u state and the predissociation J. Chem. Phys. 94, 2600 (1991); 10.1063/1.460690SubDoppler laser spectroscopy of SO2 in a supersonic beam
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.
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