Transition probabilities from the ground state of the npπ 1Πu- states of H2

The position and the intensities of the Q lines of the absorption spectrum of H-2 were studied in the 81-72nm wavelength range, using synchrotron light. The transition probabilities of the np pi(1)Pi(-)(u) v,J - X-1 Sigma(+)(g) v ''= 0, J ''= J=1 transitions with 3 <= n <= 12 have been measured and compared to calculated values. A good agreement has been found. The main discrepancies observed may well be related to local non-adiabatic couplings not included in the calculations. Vibrational couplings between levels with large Delta v values up to Delta v = 5 were observed affecting the transition probabilities.