FIR LASER STARK SPECTROSCOPY OF CH318OH

The laser Stark spectrum of O-18-substituted methanol has been studied using the 337- and 311-mum lines of the HCN laser as well as the 195- mum line of the DCN laser. Numerous families of absorption lines have been observed for both parallel and perpendicular polarizations up to 60 kV/cm. With the 337-mum line, two families of resonances are identi fied as J(K) = 96 - 10(5)E2, v(t) = 0 and J(K) = 1(1) <-- 2(2)E2, v(t) = 1 transitions. The Stark shifts for the J(K) = 96 - 10(5)E2, v(t) = 0 transition are best represented by values of 0.893 +/- 0.020 and 1. 36 +/- 0.02 D for the parallel and perpendicular components. respectiv ely, of the electric dipole moment for CH3OH-(O-18). Two families of r esonances observed at lambda = 311 mum are identified as the J(K) = 9( 1)- 8(2)+A, v(t) = 1 transition, forbidden in zero field, and the J(K) = 74 - 63A, v(t) = 0 transition. An R-branch transition observed with the 195-mum line has been identified as the J(K) = 10(7) - 9(6)A, v(t ) = 0 transition. Zero-field frequencies for all the assigned transiti ons are given with improved accuracy over those calculated from availa ble molecular constants. (C) 1994 Academic Press, Inc.