Perturbation in the V B-1(2) state of CS2 and the effects of an applied magnetic field

The excitation spectra of the 15V 31 344.9 band of the CS2 V B-1(2)<-- X (1 )Sigma(g)(+) transition and the changes in these spectra with the applicati on of a magnetic field of up to 12 kG have been measured with sub-Doppler r esolution. The radiative lifetimes of rotationally resolved single lines an d single Zeeman components were measured under collision-free conditions. A ll of the fluorescence decays were observed to be of a single exponential. Large Zeeman splittings were observed for many lines. The only symmetry all owed spin-orbit interaction is that of the (3)A(2)(B-2) component with the B-1(2) state. The (3)A(2)(B-2) component has no magnetic moment, but a magn etic moment is induced when it is mixed with the (3)A(2)(A(1),B-1) componen ts. The mixing of the (3)A(2)(B-2) and (3)A(2)(A(1),B-1) components is faci litated by spin-rotation interaction and the Zeeman interaction. From analy sis of the observed Zeeman splittings of the perturbed levels, the (3)A(2)( B-2) component was determined to lie 14 cm(-1) below the nearly degenerate (3)A(2)(A(1)) and (3)A(2)(B-1) components in the energy region where the 15 V band is observed. Irregular energy shifts and splittings of rotational li nes were observed, and these were attributed to (a) Coriolis interaction be tween the (VB2)-B-1(v(')(a(1));K=0JM) and V B-1(2)(v(b(2));K=1JM) levels an d (b) resonant spin-orbit interaction between the rotational levels V B-1(2 )(v(')(a(1));KJM) and R (3)A(2)(v(a(1));KJM). These interactions become app reciable when two levels lie close in energy. Large Zeeman splittings were observed in case (b). Many vibrational lines with irregular intensity and s pacing were observed in each band. These were attributed to (c) Fermi reson ance between the vibrational levels in the V B-1(2) state and (d) resonant spin-orbit interaction between vibrational levels in the V B-1(2) and R (3) A(2) states. In case (d), large Zeeman splittings were observed for a serie s of rotational lines in a vibrational band. The background lines were iden tified from observed Zeeman splittings as the transitions to levels of the R (3)A(2) state, which are induced by resonant spin-orbit interaction with the levels of the V B-1(2) state. The intensity of the excitation spectrum of the V B-1(2)<-- X(1)Sigma(g)(+) transition was observed to decrease as t he magnetic field increases. This was attributed to a mixing of the (3)A(2) state with the V B-1(2) state and the resulting triplet-triplet emission, which was not detected in this experiment. It was possible to evaluate the lifetime of the radiative triplet-triplet emission via deperturbation analy sis of the perturbed lines. (C) 2000 American Institute of Physics. [S0021- 9606(00)00525-0].