Time and spatially resolved atomic absorption measurements with a dye laser plume atomizer and pulsed hollow cathode lamps

Abstract

Time and spatially resolved atomic absorption measurements were made using a -µß dye laser beam to atomize solid samples of Cu, Al, and Pb alloys, steel, and graphite. Pulsed hollow cathode lamps with pulses as short as 1 ps were used as primary sources for the atomic absorption measurements. The Influences of sample chamber pressure were studied. The time-integrated, absorption spectral line profile of Cu In the plume was observed during the first 60 ps of the plume.Intense focused laser beams have been used as atomizers for atomic absorption spectroscopic analysis of solid samples by several investigators (1-7). Mossotti et al. (1) and Piepmeier (2) used Q-switched lasers to atomize the sample, and flash lamps as the primary light source. Karyakin and Kaigorodov (3) took advantage of the intense radiation emitted from the laser plume itself as the primary source and used the widths of self-reversed lines produced on film as an analytical signal. Osten and Piepmeier (4) and Vul'fson et al. (5) used pulsed hollow cathode lamps as primary sources. Hollow cathode lamps operated in the dc mode have been used as primary light sources by Matousek and Orr (6), who used a graphite furnace to aid atomization by a C02 TEA laser, and by Ishizuka et al. (7), who swept the atomized sample into an auxiliary observation chamber by a rapid flow of argon gas. The graphite furnace (6) and the auxiliary observation chamber (7) were designed to mask emission signals from the plume, which interfere with the observation of the absorption signal. The masking effectively reduced the plume emission signals relative to the dc hollow primary source signals, but did not entirely eliminate sample emission in all cases.Piepmeier and Osten (8) predicted from theoretical considerations that the intense continuum emission from the plume could be reduced by using a long laser pulse [of the same energy], and by using a laser with a shorter wavelength to reduce inverse Bremsstrahlung absorption of the laser energy in the plume, which tends to result in intense plasma emission. This study reports the results of using such a laser to atomize solid samples, and using long and short-pulse hollow cathode lamps as primary sources. The influence of the pressure of the gas in the sample chamber is studied. EXPERIMENTAL Laser Microprobe. The laser used in these experiments was a Chromabeam 1070 dye laser (Synergetics Research, Inc.). The lasing dye solution (1 X 10"4 M Rhodamine 6B in 95% ethanol) was circulated through the 1-cm bore of a coaxial flash lamp. The maximum energy for the l-µß laser pulse was 0.1 J. The maximum repetition rate was 3 pulses per min.The original laser trigger used an electromechanical relay in the primary circuit of a high voltage pulse transformer, similar to that used in a conventional automobile ignition system. The secondary circuit of the transformer was connected to the trigger

Acoustic signal as an internal standard for quantitation in laser-generated plumes

“…This technique will be especially valuable as an internal standard for normalization in depth profiling and in other LMA experiments in which the laser output, sample conditions, and other experimental parameters vary substantially. In this work only the emission signal was monitored, but application of this normalization procedure could be easily extended to other spectroscopic techniques like atomic absorption (45) and fluorescence (46) and to cases where the ablated material is swept to another location (47) or redeposited onto a collector for further excitation (48).…”

Basic investigations for laser microanalysis: II. Laser-induced fluorescence in laser-produced sample plumes

“…Of course, this principle is also valid in microanalysis applying laser atomization. With an appropriate time-delay, the laser-ablated plume can be reexcited by highvoltage sparks [1], microwave and radio-frequency discharges [2,3,4] or in an inductively coupled plasma [5,6]; the atomic absorption by the plume of narrow band-width radiation can be measured [7,8] or the atoms in the vapour cloud can be selectively excited by tunable, narrow band-width laser radiation in order to record the fluorescence photons. Laser-induced fluorescence (LIF) is known as a very selective and sensitive method for spectrochemical analysis [9,10].…”

New techniques in atomic and molecular laser spectroscopy

“…This material has found utility as an analytical sample source. The vapor cloud has been analyzed by a number of different techniques, some of which include emission (93,123,124,125), direct absorption (95,126,127,128), absorption after being swept into a secondary flame source (129), fluorescence (130), and mass spectral analysis (131). The transient nature of these vapor plumes complicates fundamental studies on their formation and decay.…”