Research Of The Long-pulsed Laser Induced Breakdown Pb/Cr Spectroscopy

As a new method of spectroscopy,Laser induced breakdown spectroscopy(LIBS)has advantages such as rapid analysis,on-line analysis in hostile environments and non-destructive analysis.However,the LIBS technique still has vulnerabilities in such grounds as low accuracy and low sensitivity.Studying the enhancement mechanism of laser induced plasma and improving the accuracy and sensitivity has important scientific significance and application value.A long-pulsed laser,Q-switched laser and millisecond pulsed laser are focused on Cr and Pb-doped soil samples and HPb59 brass alloy samples respectively.And by drawing the calibration curves and calculating the limit of detection and obtaining the parameters characterizing a laser-induced plasma,the influence of laser pulse width,spectrum characters and self-absorption on laser induced breakdown spctroscopy has been researched and the effect of long-pulsed laser on enhancement of laser induced breakdown spectroscopy has been studied.First,plasma is generated by focusing a long-pulsed(80 ?s)laser and Q-switched(18 ns)laser on soil samples respectively.The calibration curves of Cr are drawn,limit of detection is caculated,plasma temperature and electron density are obtained.And the enhancement effect and mechanism of laser induced plasma have been contrastive analysed.It is indicated that the limit of detection is decreasing 19 %,plasma temperature and electron density are increasing 75 % and 24 % respectively compared with that induced by a Q-switched laser.In conclusion,the sample plasma can be excited by the trailing edge of long-pulsed laser with the increasing of number of exciting particle and electron density.The long-pulsed laser has an obvious effect on improving the quality of the spectra and accuracy of analysis of element.Meanwhile it is showed that enhancement of millisecond pulse laser induced breakdown Pb,Cr spectroscopy is unconspicuous compared to the long-pulsed laser(80 ?s).Second,alloy plasma is generated by the long-pulsed(80 ?s)laser.The calibration curves of Pb are drawn and limit of detection is caculated and plasma temperature and electron density are obtained.It is indicated that the limit of detection is decreasing66 %,plasma temperature is increasing 72 % and electron density in different samples are increased 32-120 % respectively compared with that induced by a Q-switched laser.In conclusion,better excited result is obtained in long-pulsed laser induced alloy plasma,which improve the analysis of laser induced breakdown alloy spectroscopy.At last,the different characters of spectra of heavy metal elements in soil sample and self-absorption properties of Cu in alloy sample are analyzed with spectrum line transition probability,atomic configuration,angular momentum and atomic configuration.It is showed that in soil sample SBR of the heavy metal element spectral line is independent on transition probability,the variation in SBR with element content exhibits similar characteristics for the lines with same atomic configuration and the excitation of lines with large angular momentum is better with higher regression coefficient of calibration curves.And it is indicated in alloy sample extents of self-absorption of Cu atomic lines decrease with increasing observation time;within the limit,the self-absorption shows an increase of extents with the increase of energy,and to the spectra lines with the same atomic configuration,extents of self-absorption at spectral lines with large angular momentum are more sensitive with a higher value of extent change and a longer duration.As the self-absorption can be ignored,choosing the spectra with large angular momentum as analysis lines is beneficial to improve the sensitivity of LIBS.