Laser spectrometry

Photodiode detectors have already been cited in this chapter in relation to near-IR fluorescence measurements on singlet oxygen,(8 16 18) in decay-time temperature sensing,(50) in liquid chromatography,(62) the study of proteins labelled with Nile Red,(64) and diode laser spectrometry,(67) Photodiodes are also conveniently packaged for many applications in an array form enabling rapid data acquisition e.g., in spectrophotometry, (35)... 

Sauke, T.B. Becker, J.F. Loewenstein, M. Gutierrez, T.D. 8c Bratton, C.G., An Overview of Isotope Analysis Using Tunable Diode Laser Spectrometry Spectroscopy 1994, 9(5), 34-39. 

Lantzsch et al. [20] and Arslan et al. [21] have carried out trace determinations of "strontium and "strontium in solid samples using laser spectrometry combined with mass spectrometry [16] and accelerator mass spectrometry [17]. 

Since their invention in 1960, lasers have made a significant impact in chemistry. Fundamental and applied spectroscopy have been major benefactors of the new laser technology. Analytical laser spectrometry is currently a vital and growing field of research. 

The selection of the best analytical line has not been discussed explicitly and deserves attention. Because LEI is at least a two-step process involving laser excitation and thermal ionization steps, many transitions may be preferred for LEI which are not usable by purely optical methods. In other words, excited states which have low fractional populations may produce good LEI sensitivity due to proximity of the laser-populated state to the ionization potential. This makes the choice of the most sensitive LEI lines more complicated but it introduces an important practical advantage for dye laser spectrometry. 

Miclea M., Kunze K., Musa G., Franzke J. and Niemax K. (2001) The dielectric barrier discharge - a powerful microchip plasma for diode laser spectrometry, Spectrochim Acta, Part B 56 37-43. 

Stacknik et al, 1992), and by in-situ tunable diode laser spectrometry (May and Webster, 1989). In the 1990s, global distributions of this gas were obtained by the HALOE infrared instrument aboard UARS (Russell et al., 1993 Figure 5.59). The distribution and variability of the total column abundances of HC1 have been reported, for example, by Mankin and Coffey (1983). 

Kerstel ERT, varr Tri R, Dam N, Reuss J, Meijer HAJ (1999) Simrrltaneous determirration of the H/ h, arrd 0/ 0 isotope abundance ratios in water by means of laser spectrometry. Arralyt Chem... 

Fig. 1. Experimental setup for the optical absorption measurement of size-selected cluster ions by the photodissociation laser spectrometry.

The UFg detector based on laser spectrometry (UFLS) is an on-site analytical instrument based on TDLS. It measures the enrichment of UFe samples (Lebrun et al. 2008). The system has passed feasibility study and is now under development for field use. It determines the concentration of and in UFg on-site with an accuracy of greater than 1% for enrichment. The precise measurement of the isotopically broadened absorption peaks of and requires a mid-IR laser with wide single-mode tuning ranges, better than 4 cm of continuous tuning at 1,290 cm and less tuning at 852 cm . In comparison with mass spectrometry, UFLS does not require a highly trained specialist to perform measurements. It is hoped that the instrument will partly replace the need for DA and thereby will improve verification timeliness and reduce inspection resources. 

Every effort is made here to achieve the highest possible absolute power of detection. Microdistribution analysis represents the primary field of application for microprobe techniques based on beams of laser photons, electrons, or ions, including electron microprobe analysis (EPMA), electron energy-loss spectrometry (EELS), particle-induced X-ray spectrometry (PIXE), secondary ion mass spectrometry (SIMS), and laser vaporization (laser ablation). These are exploited in conjunction with optical atomic emission spectrometry and mass spectrometry, as well as various forms of laser spectrometry that are still under development, such as laser atomic ab.sorption spectrometry (LAAS), resonance ionization spectrometry (RIS). resonance ionization mass spectrometry (RIMS), laser-enhanced ionization (LEI) spectrometry, and laser-induced fluorescence (LIF) spectrometry [36]-[44],... 

In non-laser desorption/laser ionisation techniques selective laser ionisation of gas phase neutrals (atoms and molecules), generated by evaporation, thermal heating, particle or photon bombardment, can be applied. Regarding ionisation, it is possible to differentiate between thermal impact with other particles (LEIS laser-enhanced ionisation), ionisation due to an electric field (FILS field ionisation laser spectrometry) and that due to photoionisation (RIS resonance ionisation spectrometry). This type of ionisation can be combined with a mass spectrometer to detect isotopes selectively (RIMS resonance ionisation mass spectrometry). If a polymer additive is volatile enough its presence can be ascertained via ionisation-only spectra. That is, the additive evaporates from the near-surface region for a certain amount of time, and the ionisation laser alone will yield a reasonable amount of signal to obtain an analysis of the additive present. 

Ab initio calculations have been made of the vibrational wavenumbers of the radicals XSO and XSO2 (X = F or Cl) in the ground and excited states. Tunable diode laser spectrometry gave data on line intensities for the V1+V3 band of S02. Revised vibrational assignments have been proposed for the fluorosul-fite ion, S02F. Values for the Cs salt are given in in Table 18. ... 

The instrumentation on board the Citation aircraft has been described by J. Lelieveld et al. [Geophysical Research Letters, 104 8201 (1999)]. On the Citation, C-130 air-craft, and the RW Brown, CH3CN and CH3C(0)CH3 have been measured by proton-transfer-reaction mass spectrometiy, as described by W. Lindinger, A. Hansel, and A. Jordan [International Journal of Mass Spectrometry and Ion Processes, 173 191 (1998)]. On the C-130 aircraft, these gases and SO2 were also measured by chemical ionization mass spectrometry. On the Citation aircraft, CO was measured by tunable diode laser spectrometry (TDLAS), as described by F.G. Wienhold et al. [Journal of Applied Physics, B67 411 (1998)] on the RW Brown, CO was measured by TDLAS, as described by H. Fischer et al. [Journal of Geophysical Research, 102 23559 (1997)]. 

---