Isotope selective spectroscopy

In combination with mass spectrometry isotope selective spectroscopy becomes possible, even if the spectral lines of the different isotope spectra... 

In summary, NIS provides an excellent tool for the study of the vibrational properties of iron centers in proteins. In spectroscopies like Resonance Raman and IR, the vibrational states of the iron centers are masked by those of the protein backbone. A specific feature of NIS is that it is an isotope-selective technique (e.g., for Fe). Its focus is on the metal-ligand bond stretching and bending vibrations which exhibit the most prominent contributions to the mean square displacement of the metal atom. 

This chapter is concerned with experimental investigations of the dynamics of the dissociation of polyatomic neutral molecules carried out by the technique of laser Doppler spectroscopy, in bulk and under crossed-beam condition. Photodissociation is a basic process in the interaction of light with molecules, of interest in itself as an elementary molecular process and also with respect to a variety of applications in different fields. The interest has increased considerably in recent years, first, because the experimental investigation of photodissociation is rapidly advancing by the use of the laser, and second, because the laser makes possible to achieve photodissociation, state, and isotope selectively, by new excitation mechanisms. These are, aside from the common one-photon absorption, stepwise... 

Fig. 1.16 Isotope-selective intracavity absorption spectroscopy. The frequencies (Ok absorbed by the isotope inside the laser cavity are missing in the laser output, which therefore does not excite any fluorescence in the same isotope outside the laser resonator [20]...

When used in combination with mass spectrometry, RTPI allows mass- and wavelength-selective spectroscopy, even if the spectral lines of the different species overlap. This is particularly important for molecular isotopes with dense spectra, which overlap for the different isotopes. This is illustrated by Fig. 1.40, where the differences in the line positions in the spectra of Li3 and Li3 are caused partly by the different masses but mainly by the different nuclear spins. Such isotope-selective spectra give detailed information on isotope shifts of vibrational and rotational levels and facilitate the correct assignment of the spectral lines considerably. Furthermore, they yield the relative isotopic abundances. 

V. Beutel, H.G. Kramer, G.L. Bahle, M. Kuhn, K. Weyers, W. Demtrdder, High resolution isotope selective laser spectroscopy of Aga molecules. J. Chem. Rhys. 98, 2699 (1997)... 

Isotope-Selective Elemental Analysis by High-Resolution Laser Spectroscopy... 

The isotope-selective analysis by optical detection methods is almost impossible unless transitions with sufficiently large isotope shifts as observed with light and heavy elements are available. In contrast to traditional emission or absorption techniques the high-resolution laser spectroscopy enables Doppler-free measurements since the spectral linewidth of tunable CW lasers is commonly less than the Doppler profile... 

The narrow spectral line of a DL enables isotope selective analysis. For light and heavy elements (such as Li and U) the isotope shifts in spectral lines are often larger than the Doppler widths of the lines, in this case isotopically selective measurements are possible using simple Doppler-limited spectroseopy - DLAAS or laser induced fluorescence (LIF). For example, and ratios have been measured by Doppler-limited optogalvanic. spectroscopy in a hollow cathode discharge. DLAAS and LIF techniques have been combined with laser ablation for the selective detection of uranium isotopes in solid samples. This approach can be fruitful for development of a compact analytical instrument for rapid monitoring of nuclear wastes. 

In this section special interest is focused on the intersection of the intersystem crossing of the K2 A state with the b 77u state. Applying one-color pump probe spectroscopy with a wavelength of 833.7 nm, the wave packet dynamics of around = 12 is studied. Isotope-selective detection... 

Magnetic hyperfine fields observed by Mbssbauer spectroscopy are useful information to characterize condensed matters. If a sample includes a certain amount of Fe or Sn, Mbssbauer measurements are easily applied. If the sample is able to be enriched with Mbssbauer isotope Fe or Sn, the limit of concentration required for the measurements can be greatly reduced. Specific samples for interface studies are prepared by doping with isotope selectively at the interface sites. In this article, several examples of Mbssbauer studies using interface-selectively enriched samples are introduced. 

All hyperfine parameters of the atoms near the surface can be different fi-om the hyperfine parameters of the atoms in the interior. In general, however, surface and bulk contributions are not clearly differentiated from each other. Because of the great variety of surface sites, the hyperfine parameters of the surface atoms, especially the hyperfine field, can be broadly distributed. These distributions combine with the effects of the distributions of particle size and shape, often making surface and volume effects difficult to distinguish from one another. Investigations based on the isotope selectivity of Mossbauer spectroscopy may then be particularly useful. 

There were also some remarkable meetings abroad during various scientific schools and conferences. I recall with pleasure my talks with Professor Ali Javan at the 1975 Les Houches School on Laser Spectroscopy (Fig. 14.12), and with Professor A. Siegman during my visit to Stanford University (Fig. 14.13), where we discussed animatedly the effect of isotope-selective multiple-photon dissociation of polyatomic molecules by IR laser pulses. At regular international conferences on laser spectroscopy and atomic... 

As the isotope shifts are often larger than the Doppler broadening, signals of different isotopes such as U and can often be differentiated, making isotopic analyses of enriched uranium possible [299]. Doppler-free spectroscopy with two laser beams in co- or counter-propagating directions can also be applied, which becomes even more isotopically selective, as isotope patterns hidden in the Doppler profile can then be visualized. 

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