Atomic and molecular ion emission from silica in laser microprobe mass analysis (LAMMA): Comparison with secondary ion mass spectrometry (SIMS) and spark source mass spectrometry (SSMS)

Abstract

Irradiation of silica with a frequency quadrupled Q-switched Nd-YAG laser pulse produces Si m ± and Si mO n ± ions of mass up to about 600 amu. The experimental molecular ion distributions in LAMMA are similar to those observed in SIMS and SSMS, although data are only available for m values up to 5 and 3, respectively. Maximum intensity is observed, for a given value of m, at Si mO 2m-2 + (m=1, 2 or 3), at Si mO 2m-1 + (m=4, 5 or 6) or at Si mO 2m + (m⩾7) and the positive ion yields can be described by a Gaussian distribution, when plotted as a function of the “fragment valence”. Negative ion yields show Si mO 2m+1 − and Si mO 2m − as especially stable forms. The LAMMA results are compared with those of SIMS and SSMS.