ANALYSIS OF THE MOLECULAR BANDS OF D2H AND H2D AT 5600 ANGSTROM

Spectral simulation was used to analyze the molecular rovibrational ba nds of D2H and H2D at 5600 Angstrom. These bands were previously measu red by the ion beam neutralization method. They were assigned to the e lectronic 3p(2)B(1) -2s(2)A(1) and vibrational (v - v '') = (0,0,0,- 0 ,0,0) tran sitions. Least squares fits to the experimental line-positi ons were made to determine the asymmetric rotator constants A, B and C for the 2s(2)A(1) and 3p(2)B(1) v = 0 states of D2H and H2D, hitherto unknown. Lorentz line-profiles were assumed for the D2H and H2D rotat ional lines, whose widths are mainly governed by the lifetimes of the lower states. The bands at 5600 Angstrom were simulated and the 2s(2)A (1) state lifetimes were estimated to be sigma greater than or equal t o 0.5 +/- 0.2 ps for D2H and sigma greater than or equal to 0.4 +/- 0. 2 ps for H2D. Vibrational constants of D-3 and D2H in the 2s(2)A(1) st ates are determined from the positions of the 0-0 and 0-1 vibrational bands given in respective experimental spectra previously measured. Fo r the first time the vibrational constants omega(1) and omega(2) of th e 2s(2)A(1) state of H2D were estimated from the positions of the 0-0 and 0-1 band maxima. These vibrational constants are compared with the corresponding vibrational constants of their ions.