Atomic beam laser spectroscopy

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. 

A considerable extension of the ABMR measurements in the alkali elements, discussed above, was obtained by the introduction of the atomic-beam laser experiments at ISOLDE. With this method the nuclear quadrupole moments could be reached by studying the hfs of the excited state, as well as the IS in the isotopic sequences studied. A number of nuclear spins and magnetic dipole moments was also added. Of particular importance was the discovery of the Dj optical line in francium which opened the way to hfs and IS measurements in this element. The atomic-beam laser spectroscopy works at ISOLDE on the alkali elements 3,Rb, 55CS and Fr have been presented in Refs. [20-25]. 

The first hfs measurements in francium were made with the ABMR method, giving nuclear spin values for the sequence of isotopes - 5.22o-222pj. 2], These experiments were followed by atomic-beam laser experiments [23] which, after the identification of the Dj qitical line, gave results on the hypeifine structure constants in the 7s ground state and the 7p excited state as well as isotope shifts in 208-2i3Fr. Fuller measurements in francium include the nuclear spin of Fr, the nuclear g-factor of Fr and the electronic g-factor of francium by the ABMR method [13], the identification of the D, optical transition by atomic-beam laser spectroscopy [24], and the 7s —> 8p and 7s -> 8p Pj transitions... 

Obviously, at that time Ingvar was doing experimental physics and designing new instruments for his experiments. And he has continued to work as an experimentalist and supervise experimental work in atomic beam resonance spectroscopy, laser spectroscopy and environmentally oriented applications, but theoretical work has become an increasingly large part of his scientific activity. Indeed, so much so that in a selective list of his publications that I have obtained, only theoretical publications are mentioned Also, the nuclear physics has to a large extent given way to atomic physics in his research. 

The combination of collinear fast-beam laser spectroscopy and P-RADOP (radiation-detected optical pumping) has been used to measure nuclear spins and moments of neutron-rich isotopes of the light alkali elements jLi [72-74] and Na [75]. Here, the optically pumped fast atomic beam is implanted into a single crystal placed in a static magnetic field. The NMR signal is destroying the nuclear polarization detected by measuring the p-decay asymmetry. 

With laser beams, the effect can be observed in absorption. This is the basis for collinear fast-beam laser spectroscopy. Among the Doppler-free techniques (described in Part A, Chapter 15 by W. Demtroder) it is the only one using linear absorption without velocity selection as in collimated atomic beams. 

R. Neugart Collinear f ast-beam laser spectroscopy, in Progress in Atomic Spectroscopy Pt.D, ed. by H.K. Beyer, H. Kleinpoppen (Plenum, New York 1987) p.75... 

The development of fast ion beam laser spectroscopy techniques (for short FIBLAS) is not so unusual a case of simultaneous but independent technical evolution both in atomic and molecular physics. Although the concepts involved in both cases were quite similar, the apparatus used in the pioneering experiments were widely different, ranging from the table top mass spectrometer for the early molecular physics work to the largest tandem Van de Graaff accelerators for some of the atomic physics experiments. ... 

Fast-Beam Laser Spectroscopy on Radioactive Isotopes in the Rare-Earth Region, Oak Ridge, 1982, CERN-EP/82-80, 18 June 1982 F. Buchinger, A.C. Mueller, B. Schinzler, K. Wendt, C. Ekstrom, W. Klempt, R. Neugart, Fast-beam laser spectroscopy on metastable atoms applied to neutron-deficient ytterbium isotopes, Nucl. Instr. Meth. (1982, to be published). 

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. 

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. 

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 rest of the apparatus is the same as when operated at the Proton Synchrotron. First tested on cesium [ HUB 78 ], [ THI 81 ] the apparatus was used to uncover the resonance lines of francium for which no optical transition had ever been observed. The CERN on line mass separator, Isolde, makes available a source of more than 10 atoms/sec of chemically and isotopically pure 213 Fr isotope. Such an amount is more than needed for a laser atomic beam spectroscopy. The first step is obviously to locate the resonance line at low resolution, using a broad band laser excitation. In a second step, once the line is located, a high resolution study is undertaken, [ LIB 80] and [ BEN 84]. The observed signal is displayed (fig 3a) at low resolution and(3 b)at high resolution. 

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. 

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. 

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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