Development of laser excited atomic fluorescence and ionization methods

Progress report: May 1, 1988 to December 31, 1991. The research supported by DE-FG05-88ER13881 during the past (nearly) 3 years can be divided into the following four categories: (1) theoretical considerations of the ultimate detection powers of laser fluorescence and laser ionization methods; (2) experimental evaluation of laser excited atomic fluorescence; (3) fundamental studies of atomic and molecular parameters in flames and plasmas; (4) other studies

An expression for the atomic fluorescence and thermal-emission intensity under conditions of near saturation and arbitrary self-absorption

An expression for the effect of self-absorption on the fluorescence and thermal emission intensities is derived by taking into account stimulated emission. A simple, idealized case is considered, consisting of a two level atomic system, in a flame, homogeneous with respect to temperature and composition, and uniformly illuminated by an external quasi-continuum radiation source

Energy transfer between glucose and Dysprosium(III) in aqueous solution

The fluorescence of Dy(III) and other lanthanides is enhanced when glucose is present in the solution and the solution has been heated (15 min at 175°C). The experimental evidence suggests that this is due to energy transfer between the aldehyde formed when glucose is heated and Dy. This effect was used for glucose determination in aqueous solution. A detection limit of 7 M was obtained, with a linear response to 1 mM

A review and tutorial discussion of noise and signal-to-noise ratios in analytical spectrometry—III. Multiplicative noises

In this review, signal-to-noise ratios are discussed in a tutorial fashion for the case of multiplicative noise. Multiplicative noise is introduced simultaneously with the analyte signal and is therefore much more difficult to reduce than additive noise. The sources of noise, the mathematical representation of noise, and the major types of noises in emission and luminescence spectrometry are discussed. If the limiting source of noise is multiplicative white noise, the signal-to-noise ratio for optimal sampling time τs increases as the square root of the response or integration time of the readout and is independent of the rate at which sample and reference are measured. The variation of multiplicative flicker noise with variation in sampling time, τs, time interval between sample and reference measurements, T, and response (τr) or integration (τi) time is discussed in some detail. The optimal system for the case of multiplicative noise is a dual channel approach in which the sample and reference are measured simultaneously and a ratio of signals is taken. Although the best reference in most cases of interest to analytical chemists is a calibration standard, it is often impossible to measure a sample and a calibration standard simultaneously and so an internal standard, a detector monitoring the source intensity, etc., may be useful

Level populations in a laser-induced plasma on a lead target

Time-resolved measurements of the intensity variation of five lead atomic lines at 357.275, 363.958, 367.151, 368.348 and 373.994 nm along the height of a laser-induced breakdown spectroscopy (LIBS) plasma on a solid target at standard atmospheric conditions were made. After background correction, peak stripping of the 367 and 368 nm lines and integration over the line profiles, the temporal and spatial development of the populations of the levels from which the five lines originate were calculated. The spatial and temporal population distributions indicated that these levels were not under equilibrium conditions with respect to one another for the majority of measurements. Spatial and temporal excitation temperatures of the order of 14 000 K were obtained from Boltzmann plots, but the validity of these values should be treated with skepticism in light of nonequilibrium thermodynamic conditions. © 1997 Elsevier Science B.V.Articl