Continuum- and bound-state pair absorption in Cs-Cs, Rb-Rb and Cs-Rb systems
摘要
The absorption spectra of pure Cs and Rb vapours and a mixture of both have been measured in the wavelength region from 2300 to 3100 AA (photoionisation continuum of the atoms) in the temperature range from 410 to 540 degrees C. Pronounced absorption bands can be detected in this wavelength region. Because the absorption was found to depend proportionally on the product of the number densities of the associated atoms (N Cs 2 , N Rb 2 and N Cs N Rb ) and the energies of many observed bands correspond roughly to the sum energies of two electronically excited species, the bands are interpreted in terms of simultaneous excitation of two atoms due to the absorption of one photon ('continuum-state absorption'). For the Cs-Cs and the Cs-Rb systems analogous bands were also observed within the discrete spectra of the atoms involved ('bound-state absorption'). Enhancement of the cross section for pair absorption near dipole-allowed transitions was found in agreement with theoretical predictions.