[1] [1] M Owens, V Majidi. Effects of high-pressure buffer gases on emission from laser-induced plasmas[J]. Appl Spectrosc, 1991, 45(9): 1463- 1467.

[2] [2] W Sdorra, K Niemax. Basic investigations for laser microanalysis: III. Application of different buffer gases for laser-produced sample plumes[J]. Mikrochim Acta, 1992, 107: 319-327.

[3] [3] Shen Yueliang, Li Xu, Liu Yaming, et al.. Study on plasma characteristics of fly ash in different gas environments[J]. Chinese J Lasers, 2014, 41(5): 0515002.

[4] [4] Chen Jinzhong, Chen Zhenyu, Ma Ruiling, et al.. Effect of spatial confinement of carbon sheets on the soil plasma radiation characteristics [J]. Chinese J Lasers, 2013, 40(1): 0115002.

[5] [5] V N Rai, A K Rai, F Y Yueh. Optical emission from laser-induced breakdown plasma of solid and liquid samples in the presence of a magnetic field[J]. Appl Opt, 2003, 42(12): 2085-2093.

[6] [6] X K Shen, J Sun, Y F Lu, et al.. Spatial confinement effects in laser-induced breakdown spectroscopy[J]. Appl Phys Lett, 2007, 91(8): 081501.

[7] [7] X K Shen, J Sun, Y F Lu, et al.. Spectroscopic study of laser-induced Al plasmas with cylindrical confinement[J]. J Appl Phys, 2007, 102(9): 093301.

[8] [8] Chen Jinzhong, Zhang Xiaoping, Guo Qinglin, et al.. Study of enhancement effect of laser-induced crater on plasma radiation[J]. Spectroscopy and Spectral Analysis, 2009, 29(2): 483-487.

[9] [9] Wang Li, Xu Li, Zhou Yu, et al.. Dual-pulse laser-induced breakdown spectroscopy of Al element in AlCl3 aqueous and mixed compound solutions[J]. Chinese J Lasers, 2014, 41(4): 0415003.

[10] [10] Gao Xun, Shao Yan, Du Chuang, et al.. Pre-ablation laser parameters effect on the spectral enhancement of double pulsed laser-induced breakdown spectroscopy[J]. Chinese J Lasers, 2013, 40(8): 0815003.

[11] [11] Zhang Qiao, Hu Zhenhua, Ding Lei, et al.. Study on the liquid jet dual pulse laser-induced Ca plasma emission spectroscopy[J]. Chinese J Lasers, 2013, 40(2): 0215002.

[12] [12] C Aragon, J A Aguilera, F Penalba. Improvements in quantitative analysis of steel composition by laser-induced breakdown spectroscopy at atmospheric pressure using an infrared Nd∶YAG laser[J]. J Appl Spectrosc, 1999, 53(10): 1259-1267.

[13] [13] C Aragon, J Bengoechea, J A Aguilera. Influence of the optical depth on spectral line emission from laser- induced plasmas[J]. Spectrochimica Acta Part B, 2001, 56(6): 619-628.

[14] [14] Chen Jinzhong, Ma Ruiling, Wang Jing, et al.. Study of self-absorption effect on laser-induced metal plasma[J]. Spectroscopy and Spectral Analysis, 2014, 34(9): 2337-2341.

[15] [15] X J Su, W D Zhou, H G Qian. Optimization of cavity size for spatial confined laser-induced breakdown spectroscopy[J]. Opt Express, 2014, 22(23): 28437-28442.

[16] [16] Zhao Zhi. Spectroscopy Characterization of Keyhole Plasma during Deep Penetration Laser Welding[D]. Changsha: Hunan University, 2009.