Laser spectroscopy atomization

Sneddon, J., Thiem, T. and Lee, Y.-I. (1997) Lasers in Atomic Spectroscopy, John Wiley, New York. 

Laser spectroscopy is such a wide subject, with many ingenious experiments using one or two CW or pulsed lasers to study atomic or molecular stmcture or dynamics, that it is difficult to do justice to it at the level at which Modern Spectroscopy is aimed. In this edition 1 have expanded the section on supersonic jet spectroscopy, which is an extremely important and wide-ranging field. 

In dimers composed of equal molecules the dimer components can replace each other through tunneling. This effect has been discovered by Dyke et al. [1972] as interconversion splitting of rotational levels of (HF)2 in molecular beam electric resonance spectra. This dimer has been studied in many papers by microwave and far infrared tunable difference-frequency laser spectroscopy (see review papers by Truhlar [1990] and by Quack and Suhm [1991]). The dimer consists of two inequivalent HE molecules, the H atom of one of them participating in the hydrogen bond between the fluorine atoms (fig. 60). PES is a function of six variables indicated in this figure. 

Figure 4.21 Evidence for the hot atom concept from ionisation laser spectroscopy.

Electron diffraction spectroscopy ETA LEAFS Electrothermal atomisation laser-excited atomic fluorescence... 

Hinkl, E. D., K. W. Nill, and F. A. Blum. Infrared spectroscopy with tunable lasers, pp. 125-1%. In H. Walther, Ed. Laser Spectroscopy of Atoms and Molecules. New York Springer-Verlag, 1976. 

COLLISIONAL ENERGY-TRANSFER SPECTROSCOPY WITH LASER-EXCITED ATOMS IN CROSSED ATOM BEAMS A NEW METHOD FOR INVESTIGATING THE QUENCHING OF ELECTRONICALLY EXCITED ATOMS BY MOLECULES... 

Collisional Energy-transfer Spectroscopy with Laser-excited Atoms in Crossed Atom Beams A New Method for Investigating the Quenching of Electronically Excited Atoms by Molecules... 

Hyperfine structure measurements using on-line atomic-beam techniques are of great importance in the systematic study of spins and moments of nuclei far from beta-stability. We will discuss the atomic-beam magnetic resonance (ABMR) method, and laser spectroscopy methods based on crossed-beam geometry with a collimated thermal atomic-beam and collinear geometry with a fast atomic-beam. Selected results from the extensive measurements at the ISOLDE facility at CERN will be presented. 

As mentioned above, the radon and radium sequences have been investigated by collinear fast-beam laser spectroscopy, whereas in francium all three atomic-beam methods, ABMR, atomic-beam laser spectroscopy and collinear laser spectroscopy, have contributed. 

Several groups at ISOLDE are planning further improvements of their techniques. For each element the most appropriate experimental scheme has to be found. Today, collinear laser spectroscopy is the most general high-resolution and sensitive method for optical spectroscopy on radioactive beams delivered by on-line mass separators. Its sensitivity ranges from 10 - 10 atoms/s depending on the strength and multiplicity of the optical transitions. 

The schematic view of the Mainz apparatus for collinear laser spectroscopy, installed at Isolde is given in fig 4. The 60 keV ion beam is set collinear with the laser beam, then accelerated (or decelerated) and finally neutralized in charge exchange cell. By Doppler tuning the atomic absorption is set resonnant with the stabilized laser frequency, and the fluorescence emitted is detected. 

Because of the velocity bunching effect due to initial acceleration the ion beam is nearly monokinetic, and the neutralisation does not effect the velocity distribution The details of the method can be found in [ KAUF 78 ], [ NUE 78] By neutralisation in an alkali vapour, the atomic metastable states are preferentially populated since their energies match the ionisation potential of the corresponding alkali atom Therefore this technic is ideally suited for laser spectroscopy of rare gas, and is recently successfully used to study the heaviest one, radon Fig. 

The rare earth elements are different from other elements because the optical transitions between levels of the fn configuration are inherently very sharp-lined and have well-resolved structure characteristic of the local crystal fields around the ion. In minerals, this characteristic provides an excellent probe of the local structure at the atomic level. Examples will be shown from our work of how site selective laser spectroscopy can be used to determine the thermal history of a sample, the point defect equilibria that are important, the presence of coupled ion substitution, the determination of multiple phases, and stoichiometry of the phase. The paper will also emphasize the fact that the usefulness and the interpretation of the rare earth luminescence is complicated by the presence of quenching and disorder in mineral samples. One in fact needs to know a great deal about a sample before the wealth of information contained in the site selective luminescence spectrum can be understood. 

Our research group at the University of Wisconsin has developed a new approach to the study of minerals that can provide great detail at the atomic level. Our program is founded on the idea that site selective laser spectroscopy can be used to simplify the spectra of complex materials. Recent reviews of our work are published in reference 1. The methods can be used to ... 

Decomps, B., Dumont, M. and Duclqy, M. (1976). Linear and nonlinear phenomena in laser optical pumping. In Laser Spectroscopy of Atoms and Molecules. Topics in Applied Physics, vol. 2, ed. H. Walther, pp. 283-347 (Springer-Verlag, Berlin, Heidelberg, New York). 

Continuous wave coherent Lyman-a radiation has recently become available [85] so that laser cooling or sensitive shelving spectroscopy of magnetically trapped hydrogen atoms is coming within reach. The ability to work with a small number of atoms is of particular interest for laser spectroscopy of antihydrogen, a goal pursued by the ATRAP and ATHENA collaborations at CERN [8]. 

Fig. 1. Muonium energy levels for states with principal quantum numbers n = 1 and n = 2. The indicated transitions could be induced to date using modern techniques of microwave or laser spectroscopy. High accuracy has been achieved for the indicated transitions which involve the ground state. The atoms can be produced very efficiently only in the Is state...

Abstract. Laser spectroscopy of hydrogen-like and helium-like ions is reviewed. Emphasis is on the fast-beam laser resonance technique, measurements in moderate-/ ions which provide tests of relativistic and quantum-electrodynamic atomic theory, and future experimental directions. 

Precision measurement of energy intervals in hydrogen and helium has been fundamental to the development of atomic theory. Relativistic and quantum-electrodynamic contributions scale with various powers of Z. Hence more information is gained by extending precise measurements to one- and two-electron ions. Laser spectroscopy is restricted to certain special transitions which fall in the infrared, visible or near-ultraviolet, and from which a useful signal can be obtained. However, where applicable, it provides precision tests of theory. The focus of this review is laser spectroscopy of the n = 2 levels of moderate-Z helium-like and hydrogen-like ions. Previous reviews may be found in [1,2,3],... 

In Florence, we have chosen an approach that combines laser spectroscopy with the direct frequency measures of the microwave experiments [4]. We take advantage of the obvious consideration that to obtain the FS separations there s no need to precisely know the optical transitions frequencies but just their differences. Thus, if we have two laser frequencies whose difference can be accurately controlled, we may use one as a fixed reference and tune the second across the atomic resonances, as illustrated by Fig. 1. In fact, our approach reverts to an heterodyne technique, where all the transitions are measured with respect to the same reference frequency, that can take any arbitrary but stable value. In the experimental realisation we obtain the two frequencies by phase-locking two diode lasers (master and slave), i.e. phase-locking their beat note to a microwave oscillator [14]. We show in Fig 2 a full-view of the experimental set-up. 

The second phase will be designed and constructed based on the results of Phase 1. While the focus is on 2-photon laser spectroscopy of magnetically trapped antihydrogen atoms, other measurements (e.g. a measurement of the hyperfine structure using an atomic antihydrogen beam) are being explored for this program. 

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