Electronic branching ratios of spontaneous emission for transitions between states of the 3d and 2p singlet complexes of terms of H-2

The ratios of probabilities (the electronic branching ratios) for the rovib ronic spontaneous transitions are for the first time measured for transitio ns from the rotational levels with J' less than or equal to 6 of the I(1)Pi (-)(g) v' = 0-2 and J(1)Delta (-)(g), v' = 0 states to the vibrational-rot ational levels of different low-lying electronic states B(1)Sigma (+)(u), v ", J' anti C(1)Pi (-)(u), v"', J' - 1 of the H-2 molecule (for the vibratio nal quantum numbers v" less than or equal to 4 and v"' less than or equal t o 2). Values of these quantities provide a new channel of information on th e internal structure of the hydrogen molecule thus far unused and should be particularly sensitive to the adiabatic values of the electronic transitio n dipole moments. Tn studying the entire set of rovibronic radiative transi tions, they may significantly add to the experimental data on rovibronic te rms, radiative lifetimes, and vibrational and rotational branching ratios u sed before. The experimental data obtained are compared to the correspondin g values derived from the results of an earlier semiempirical determination and ab initio calculation of the absolute transition probabilities. Our ex perimental data are in remarkable agreement with the semiempirical results and significantly differ from the ab initio results. This fact directly sug gests the necessity of performing more accurate ab initio calculations of t he rovibronic transition probabilities for the given systems of bands. (C) 2001 MAIK "Nauka/Interperiodica".