Li K α Emission Spectrum of LiF Under Electron Beam Irradiation

ABSTRACT It is possible to obtain the Li Kα spectrum of LiF on an electron microprobe, with minimal damage, provided a low acceleration energy (1 kV) and a small current density (1 pA/μm 2 ) are used. The presented spectrum agrees with the one obtained with synchrotron radiation many years ago and is expected to be free of damage. The spectrum displays two main peaks: the first one at c.a . 47 eV coming from the electron transition from the occupied valence states toward the Li 1s core level; the second one at c.a . 62 eV giving evidence of the radiative recombination of the lithium core exciton. These features, as well as the background due to cathodoluminescence, change drastically after 1 min of electron irradiation, due to fluorine leaving the sample and the subsequent oxidation of the remaining lithium atoms in the residual atmosphere of the microprobe.