Ion beam, laser spectroscopy

Some special techniques and possible applications of fast-ion-beam laser spectroscopy (FIBLAS) are illustrated by four different groups of experiments. 

S. Abed, M. Broyer, M. Carre, M.L. GaiUard, M. Larzilliere, High resolution spectroscopy of N2O+ in the near ultraviolet, using FIBLAS (Fast-Ion-Beam Laser Spectroscopy). Chem. Phys. 74,97 (1983)... 

Microwave techniques were combined with fast ion beam laser spectroscopy (see Figure 11) in order to investigate the hyperfine structure of A 50-keV, isotopically pure ion beam with a current... 

FAST ION BEAM LASER SPECTROSCOPY OF SMALL MOLECULAR IONS... 

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. ... 

Van den Cruyce, Fast ion beam laser spectroscopy on radioactive °Ba, Hyperfine Inter. 9 193 (1981), also with G. Dumont,... 

The chapter IR Spectroscopic Techniques to Study Isolated Biomolecules gives an overview of some of the most common experimental practices currently in use to characterize the strucmre of isolated biomolecules by infrared spectroscopy. We address especially two main categories of experimental approaches conformation-selective infrared spectroscopy of jet-cooled neutral species and infrared (multiple-photon) dissociation spectroscopy of mass-selected ionized biomolecules. Molecular beam laser spectroscopy methods form the experimental basis for the topics covered in the sixth to eighth chapters. Mass spectrometry-based ion spectroscopy provided the experimental data for the studies reviewed in fourth and fifth chapters (and seventh inpart). 

The next important feature in fast beam laser spectroscopy concerns the velocity distribution. Due to kinematic velocity compression, the initial thermal distribution of velocities in the ion source is reduced by a factor R = 4cT/eV, where T is the ion source temperature and V the acceleration voltage. Including the voltage spread 6V, the Doppler width in our accelerator is 20-200 MHz, depending on mass and acceleration voltage. The transverse velocity distribution (particle wave front curvature) not affected during acceleration, contributes to the linewidth. 

In other articles in this section, a method of analysis is described called Secondary Ion Mass Spectrometry (SIMS), in which material is sputtered from a surface using an ion beam and the minor components that are ejected as positive or negative ions are analyzed by a mass spectrometer. Over the past few years, methods that post-ion-ize the major neutral components ejected from surfaces under ion-beam or laser bombardment have been introduced because of the improved quantitative aspects obtainable by analyzing the major ejected channel. These techniques include SALI, Sputter-Initiated Resonance Ionization Spectroscopy (SIRIS), and Sputtered Neutral Mass Spectrometry (SNMS) or electron-gas post-ionization. Post-ionization techniques for surface analysis have received widespread interest because of their increased sensitivity, compared to more traditional surface analysis techniques, such as X-Ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES), and their more reliable quantitation, compared to SIMS. 

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. 

In order to improve the signal-to-noise ratio in collinear laser spectroscopy, an ion source with bunched beam release was tested successfully. For this purpose, the temperature of a cold trap" inside the ion source is reduced for storage of reaction products, which are released from the trap during a subsequent period of increased temperature. The release of indium was found to occur with a FWHM of approximately 0.5s, corresponding to a... 

J. Eberz et al., "Collinear Laser Spectroscopy on l08fr)108mIn Using an Ion Source with Bunched Beam Release", to be published. 

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. 

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