Mass spectrometric studies of laser damage in calcium fluoride

Abstract

Both electron impact- and laser-ionization-mass spectrometry have been used to prove the material spalled from CaF/sub 2/ surfaces by the fundamental (1.06..mu..) and harmonic (355 nm and 266 nm) outputs from a Q-switched Nd:YAG laser. We have identified a number of gas phase products, including Ca, CaF and tentatively, CaF/sub 2/, and have measured their translational and internal energy distributions. Results suggest that while the 1.06..mu.. experiments can be adequately modeled in terms of a single damage mechanism (likely avalanche breakdown), the short-wavelength results suggest the onset of second mechanism, perhaps multiphoton absorption. This is consistent with both the observed bimodal velocity distribution following short-wavelength damage, and with the decrease in CaF vibrational and rotational excitation