کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1239755 | 1495712 | 2013 | 10 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Temperature evaluation by simultaneous emission and saturated fluorescence measurements: A critical theoretical and experimental appraisal of the approach Temperature evaluation by simultaneous emission and saturated fluorescence measurements: A critical theoretical and experimental appraisal of the approach](/preview/png/1239755.png)
• An experimental setup is constructed capable of inducing saturated ionic fluorescence within a laser-induced plasma.
• Temperatures are calculated using the saturated fluorescence signal which agrees with Boltzmann temperatures.
• Measurements are made from both resonant and excited state transitions.
• A practical discussion covers several sources for error and their experimental limitations.
Temperature is one of the most important physical parameters of plasmas induced by a focused laser beam on solid targets, and its experimental evaluation has received considerable attention. An intriguing approach, first proposed by Kunze (H.-J. Kunze, Experimental check of local thermodynamic equilibrium in discharges, Appl. Opt., 25 (1986) 13–13.) as a check of the existence of local thermodynamic equilibrium, is based upon the simultaneous measurement of the thermal emission and the optically saturated fluorescence of the same selected atomic transition. The approach, whose appealing feature is that neither the calibration of the set-up nor the spontaneous radiative probability of the transitions is needed, has not yet been applied, to our knowledge, to analytical flames and plasmas. A critical discussion of the basic requirements for the application of the method, its advantages, and its experimental limitations, is therefore presented here. For our study, Ba+ transitions in a plasma formed by focusing a pulsed Nd:YAG laser (1064 nm) on a glass sample containing BaO are selected. At various delay times from the plasma initiation, a pulsed, excimer-pumped dye laser tuned at the center of two Ba transitions (6s 2S1/2 → 6p 2P°3/2; 455.403 nm and 6p 2P°1/2 → 6d 2S1/2; 452.493 nm) is used to enhance the populations of the excited levels (6p 2P°3/2 and 6d 2S1/2) above their thermal values. The measured ratio of the emission and direct line fluorescence signals observed at 614.171 nm (6p 2P°3/2 → 5d 2D5/2) and 489.997 nm (6d 2S1/2 → 6p 2P°3/2) is then related to the excitation temperature of the plasma. Our conclusion is that the approach, despite being indeed attractive and clever, does not seem to be easily applicable to flames and plasmas, in particular to transient and inhomogeneous plasmas such as those induced by lasers on solids.
Journal: Spectrochimica Acta Part B: Atomic Spectroscopy - Volume 89, 1 November 2013, Pages 50–59