Theoretical calculations on the linewidths of rovibrational levels of the 3d Rydberg states of BeH and BeD

Rovibrational levels and widths of the positive parity 3d electronic states of BeH and BeD are calculated bl a multi-state complex scaling method. Ab initio adiabatic potential energy curves of all n = 3 Rydberg states and th e valence state C (2)Sigma(+), along with their mutual couplings (radial be tween states of the same symmetry and rotational-electronic between states differing in n by one) have been included in the calculations. The results of the seven-state calculations show extensive predissociation of the level s of all the n = 3 (2)Sigma(+) states in both BeH and BeD. The positive par ity 3p (B(2)Pi(+)) and 3d (D(2)Pi(+) and 1(2)Delta(+)) Rydberg states are a lso predissociated to differing extent, depending on the vibrational and ro tational level. Significant mixing is found among the 3d states, as expecte d, but also between the levels of 1(2)Delta nu = 0 and those of B (2)Pi nu = 2 in BeH, which in the present calculations are found to be in near coinc idence.