Structure and high-resolution IR spectroscopy of 1,2,4-triazine vapor

The high-resolution infrared bands centered at 769 and 1043 cm(-1) for 1,2, 4-triazine C3H3N3 have been analyzed, using the full asymmetric rotor Hamil ton of Watson in A-reduced form using IIIr-representation. All the ground s tate rotation constants and three of the quartic centrifugal distortion con stants could be determined with high precision from a simultaneous analysis of the two bands. The standard deviation of fit was 0.00077 cm(-1). The up per state constants for the two bands have been determined with similar pre cision. The ground state rotational constants obtained from the present ana lysis are very similar to those predicted from the ab initio study of the e quilibrium structure. This strongly suggests that the similarity in several of the ring bond lengths, predicted in the latter, is indeed real. (C) 199 8 Academic Press.