Time resolved Stark spectroscopy in NaK(B 1Π; V=1–14). Measurement of permanent electric dipole, radiative lifetimes, and collisional rate constants

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Abstract
The permanent dipole moment μ of NaK(B 1Π) has been determined for several vibrational levels by observing the electric field induced e–f mixing using either cw or pulsed laser excitation. In the latter case the spectrally resolved fluorescence decay is modulated by ‘‘Stark quantum beats.’’ We find μ(Re) =2.4 (2) Debye. The measurement of the fluorescence decay rates in zero electric field vs buffer gas pressure (rare gases, N2) yields radiative lifetimes and depopulation cross sections. The dependence of the lifetime τ with the vibrational index V can be represented by the expression: τ(V)=12.8+0.46 V ns. It is consistent with a transition dipole moment between the B 1Π and X 1Σ+ states almost independent of the internuclear distance, close to the value of the K(4P–4S) transition which corresponds to the dissociation limits of the molecular states.