Photodissociation of alkali dimers Na2and K2into atoms in ground2S and resonance2P states

The paper contains a study of photodissociation of Na 2 and K 2 molecules in ground 2 S and resonance 2 P states under conditions of continuous laser excitation of alkali vapour in the visible spectral range. Absolute effective cross section values of photodissociation have been determined, as well as their dependence on excitation frequency and vapour temperature sigma ( omega ,T). Laws governing positions of frequency peaks of cross sections and the nature of spectral and temperature dependences have been ascertained. Experimental dependences for cross sections sigma ( omega ) have been compared with theoretical calculations according to quantum mechanical and classical theory. Classical formulae for cross sections have been used for reconstruction of the potential for the B 1 Pi u state of the Na 2 molecule from obtained sigma ( omega ) dependences. Distribution of photofragments over finestructure components 2 P 3/2 and 2 P 1/2 of the resonance atomic state has been studied. Photodissociation of near-adiabatic nature has been found for atoms flying asunder at energies under 1 eV. This is manifest in the population of the 2 P 3/2 component. From an analysis of spectral dependences sigma ( omega ) and the distribution of photofragments the symmetry of molecular states has been determined, through the continuum of which the dissociation of molecules proceeds. These have been identified as B 1 Pi u and A 1 Sigma u + states.