Fluorescence emission of Ca-atom from photodissociated Ca2 in Ar-doped helium droplets. I. Experimental.

The Ca2 → Ca(4s4p 1P) + Ca(4s2 1S) photodissociation was investigated in a He droplet isolation experiment where the droplets are doped by Ar atoms. Fluorescence spectra associated with the Ca(4s4p 1P → 4s2 1S) emission were recorded as a function of the average number of Ar atoms per droplet. Three contributions were observed depending on whether the emitting Ca atoms are free, bound to helium atoms or bound to argon atoms. Moreover, the full Ca(4s4p 1P → 4s2 1S) fluorescence emission was recorded as a function of the wavelength of the photodissociation laser, hence providing the action spectrum of the Ca2 → Ca(4s4p 1P) + Ca(4s2 1S) process. The latter spectrum suggests that in He droplets doped by argon, Ca atoms are attracted inside the droplet where they associate as Ca2. Full analysis of the spectra indicate that the emission of Ca bound to a single Ar atom is redshifted by 94 cm-1 with respect to the emission of free Ca. [ABSTRACT FROM AUTHOR]