Nonadiabatic effects on the positions and lifetimes of the low-lying rovibrational levels of the GK 1Σ +g and H 1Σ +g states of H2

Abstract

The term values of rovibrational levels of the GK ¹Σ⁺_g and H ¹Σ⁺_g states of H₂ have been measured with absolute and relative accuracies down to 10⁻⁴ cm⁻¹ (≈3 MHz) and 10⁻⁶ cm⁻¹ (≈30 kHz), respectively, by measuring transitions to long-lived high-n Rydberg states using single-mode cw laser radiation and a collimated supersonic beam of cold H₂ molecules. The term values are compared with those determined in earlier experimental and theoretical investigations and the comparison points at discrepancies and a need for improved theoretical treatments of nonadiabatic, relativistic and radiative corrections for these states. The lifetimes of several low-lying rovibrational levels of the GK, H and I^{+ 1}Π_g states have been determined in pump–probe experiments. These lifetimes reveal a significant dependence on the electronic, vibrational and rotational excitation and also deviate from results obtained in earlier experimental and theoretical investigations.