Spectroscopic behavior of halogen photodesorption from alkali halides under UV and VUV excitation

The photostimulated desorption yield of neutral halogen atoms from KI, KBr, and RbI at several temperatures has been measured in the photon energy range between 5 and 30 eV using synchrotron radiation and quadrupole mass spectrometry. The features observed in the desorption yield are slightly correlated with the structures of the absorption spectra of each investigated material. The behavior of the halogen desorption yield is analyzed in the frame of inelastic electron-electron scattering processes, in close analogy with data available from the total photoelectron yield and the luminescence yield. The role played in the desorption mechanism by fundamental excitations, such as valence exciton creation and band-gap electron-hole excitation, is discussed.