THE INFRARED VIBRATION-ROTATION SPECTRUM OF THE D-3(+) MOLECULAR ION - EXTENSION TO HIGHER VIBRATIONAL AND ROTATIONAL QUANTUM NUMBERS

The assigned infrared spectrum of the D-3(+) molecular ion is extended from 84 to 529 lines by three types of spectroscopic measurements on hollow-cathode electrical discharges through deuterium gas: (i) emission from a small hollow cathode, in which the D-3(+) lines were distinguished from the electronic transitions of D-2 by the pressure dependence of their intensities; (ii) absorption in the same hollow cathode with discharge amplitude modulation; and (iii) absorption in a larger hollow cathode cell with discharge amplitude modulation. The observed lines belong mainly to the upsilon(2)(1)-0 fundamental and its hot bands 2 upsilon(2)(0)-upsilon(2)(1), 2 upsilon(2)(2)-upsilon(2)(1) and upsilon(1) + upsilon(2)(1) - v(1) in the 1330-2530 cm(-1) region in experiments (i) and (ii), and to the first overtone band 2 upsilon(2)(2) - 0 in the 3160-4000 cm(-1) region in experiment (iii). The lines were assigned by means of calculations with a large vibration-rotation basis, using a Morse-based discrete variable representation for the vibrations. This method overcomes the convergence problems for the centrifugal terms in the effective Hamiltonian approach. Six coefficients in the Meyer-Botschwina-Burton ab initio potential were adjusted in order to fit these data with a standard deviation of 0.059 cm(-1).