Laser-induced plasma generated by a 532nm pulsed laser in bulk water:unexpected line-intensity variation with water temperature and the possible underlying physics  

作　　者：Sandeep KUMARI Jeong PARK Sang-Ho NAM Song_Hee HAN Yonghoon LEE Sandeep KUMAR;朴頂;南相好;韓宋姬;李勇勳(Department of Chemistry,Mokpo National University,Jeonnam 58554,Republic of Korea;Division of Navigation Science,Mokpo National Maritime University,Jeonnam 58628,Republic of Korea)

机构地区：[1]Department of Chemistry,Mokpo National University,Jeonnam 58554,Republic of Korea [2]Division of Navigation Science,Mokpo National Maritime University,Jeonnam 58628,Republic of Korea

出　　处：《Plasma Science and Technology》2020年第7期65-74,共10页等离子体科学和技术（英文版）

基　　金：supported by the Korea Basic Science Institute(KBSI)National Research Facilities&Equipment Center(NFEC)grant funded by the Korean government(Ministry of Education)(No.2019R1A6C1010005)。

摘　　要：The effect of the matrix temperature on laser-induced plasma generated in bulk water by using a532 nm pulsed laser beam has been studied.Ca Ⅰ and Ⅱ emission line intensities were recorded for an aqueous solution of CaCl2 in the temperature range of 7℃-70℃.The emission line intensities did not follow the matrix temperature in our experiments.Maximum intensities were observed at ~18℃ for both lines.Herein,a possible mechanism responsible for the observed variation in intensity is suggested,in which laser-produced bubbles play important roles.Bubble formation is essential to ignite plasma in the liquid and more feasible at the higher liquid temperature.However,the abundant bubbles at the higher temperature can scatter the incident laser beam more effectively to decrease the energy delivered for the laser-induced plasma.Thus,these two roles have effects on the optical emission intensities in opposite ways.The validity of the suggested mechanism is discussed based on the plasma temperature,temperature dependence of the refractive index of water,plasma electron density,scattered light intensity,and plasma ignition threshold energy.Our result indicates that the temperature of the liquid is also an important parameter to be considered in the laser-induced breakdown spectroscopy analysis of bulk liquid samples and its application in deep-sea exploration.

关 键 词：laser-induced breakdown spectroscopy liquid analysis laser-produced bubble 

分 类 号：O53[理学—等离子体物理] TN24[理学—物理]