Abstract：Laser-induced breakdown spectroscopy (LIBS) is one of important methods for the composition analysis of refractory and insoluble materials. The plasma characteristics are greatly affected by the output frequency, energy, power density and focus position of laser in tests, thus influencing the accuracy of quantitative analysis. The certified reference material of soil was used as sample with Fe, Ti, Sr and Al as analysis elements and Nanosecond Nd:YAG laser device as laser light source. The laser output frequency was changed in range of 1-20 Hz, and its effect on spectrum signal-to-noise ratio (SNR), temperature, spectral line self-absorption and signal stability of plasma was investigated. The results indicated that, when other experimental conditions were fixed, the spectrum signal-to-noise ratio and temperature of plasma obviously increased with the increase of laser output frequency, while the self-absorption effect became aggravated. The relative standard deviation (RSD) of the spectral intensity of Fe I 363.360 nm was 7.16%, 7.89%, 14.89% and 11.85% when the laser output frequency was 1, 5, 10 and 20 Hz, respectively. The stability of signal showed deceasing trend with the increase of laser output frequency. The results showed that the spectral line quality of plasma could be affected by the repetition frequency. The proper laser output frequency should be selected for the analysis of elements with different contents.
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