Vibrational wave packet dynamics in NaK: The A (1)Sigma(+) state

A combined experimental and theoretical study of the vibrational wave packe t dynamics for the NaK molecule in the A (1)Sigma(+) state is presented. Th e experiment utilises a 790 nm one-colour femtosecond pump-probe scheme wit h detection of a previously nor reported dissociation pathway of the 3 (1)P i(+) state, leading to the Na(3p) + K(4s) product channel. The dissociation is suggested to proceed via either collisionally mediated processes or a m olecular cascading process via the 4 (1)Sigma(+) state, which crosses sever al states correlating to the Na(3p) + K(4s) limit. Time-dependent quantum m echanical calculations are used for studying the dynamics in detail. Simula tions are performed both for 790 nm and for 766 nm, to relate also to earli er studies. The previous interpretations of the probe processes are revised . Inclusion of vibrational and rotational temperature effects are shown to be crucial for explaining the shape of the signal and the vibrational perio d, and leads to excellent agreement with the experiments. (C) 1999 Elsevier Science B.V. All rights reserved.