A 2-COLOR (1-65,600 CM(-1) ENERGY REGION(1')+1 MULTIPHOTON IONIZATIONSTUDY OF CS2 IN THE 61,000)

The (1+1')+1 resonance enhanced multiphoton ionization (REMPI) spectru m of jet-cooled CS2 has been recorded in the 61 000-65 600 cm(-1) exci tation energy range. Four prominent band groups are observed that can be assigned to Delta nu(2)=-1 and Delta nu(2)=1 sequences of the two-p hoton electronically forbidden 4p (1'3)Delta(u) <-- (X) over tilde (1) Sigma(g)(+) transitions. Weak bands to higher energy appear to be ass ociated with the 3(0)(1), 2(0)(3) and 1(0)(1)2(0)(1) bands and corresp onding sequence bands. The results show that the upper states are not 3d Rydberg states as has been previously supposed, and are consistent with a recent reinvestigation of the corresponding (3+1) REMPI spectru m. Further experimental information is obtained on the anomalous vibra tional band structure of transitions to the 3 Delta(u), state. The 2(1 )(0) and 2(2)(1) bands of the 4p (1) Pi(u) <-- (X) over tilde (1) Sigm a(g)(+) transition are also observed, but are much weaker, suggesting that vibronic interactions are less important in this state compared t o the 4p (1,3)Delta(u) states. (C) 1995 American Institute of Physics.