Vibrational wave packet dynamics in NaK:: The A 1Σ+ state

A combined experimental and theoretical study of the vibrational wave packet dynamics for the NaK molecule in the A (1)Sigma(+) state is presented. The experiment utilises a 790 nm one-colour femtosecond pump-probe scheme with detection of a previously nor reported dissociation pathway of the 3 (1)Pi(+) state, leading to the Na(3p) + K(4s) product channel. The dissociation is suggested to proceed via either collisionally mediated processes or a molecular cascading process via the 4 (1)Sigma(+) state, which crosses several states correlating to the Na(3p) + K(4s) limit. Time-dependent quantum mechanical calculations are used for studying the dynamics in detail. Simulations are performed both for 790 nm and for 766 nm, to relate also to earlier 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 period, and leads to excellent agreement with the experiments. (C) 1999 Elsevier Science B.V. All rights reserved.