Characterization of Supersonic Gas Jets for High-Resolution Laser Ionization Spectroscopy of Heavy Elements

Abstract

The method of laser spectroscopy in supersonic gas jets was proposed for high-resolution and highefficiency in-gas laser ionization and spectroscopy studies of short-lived nuclei. The flow properties of such supersonic gas jets have been characterized under off-line conditions. Planar laser-induced fluorescence spectroscopy of seeded copper atoms has been applied to nonintrusively measure velocity, temperature, and relative density profiles of gas jets formed by different de Laval nozzles. For validation, planar laserinduced fluorescence spectroscopy was applied on supersonic free jets with well-known flow parameters. The performance of the in-gas-jet laser spectroscopy method is determined by the achievable spectral resolution, which requires an optimization and a precise manufacturing of the nozzle inner contour as well as a pressure matching of the background medium at the nozzle exit. Our studies now enable a thorough understanding and quantification of these requirements and a determination of the final performance of the in-gas-jet method. Additionally, a comparison between the experimental results and the numerical calculations was performed for the temperature, velocity, and Mach number profiles of underexpanded and quasiuniform jets formed by a de Laval nozzle.

High-precision ab initio calculations of the spectrum of Lr+

“…The gasjet method enables to accelerate the lawrencium-buffer gas mixture into a low-pressure and low-temperature jet. This in turn allows to reduce collisional broadening and thus to increase the experimental resolution [1,3]. Previous experiments proved that the gas mixture contains both atomic species, neutral as well as singly ionised Lr, wherein the fraction of the ions substantially dominates the sample composition under typical experimental conditions [4,5].…”

Laser spectroscopy of indium Rydberg atom bunches by electric field ionization

“…A set of ion optics were used to focus and accelerate the In ions to 25 keV and deflect them by 34 to overlap with two laser beams in a collinear geometry. The acceleration creates a kinematic separation in the transition frequency of the naturally abundant isotopes In (95.72%) and In (4.28%), which greatly enhances the isotope selectivity compared to in-source laser spectroscopy separation or measurement techniques 5 , 46 , laser induced breakdown spectroscopy (LIBS) 47 or in-gas cell laser ionization spectroscopy (IGLIS) 48 . Collinear ionization techniques can therefore also be used to supplement 49 the isotope selectivity of conventional mass spectrometry techniques 50 , 51 .…”

Design and commissioning of an ion guide system for In-Gas Laser Ionization and Spectroscopy experiments

“…At KU Leuven, a new laboratory has been constructed with the main goal of developing the IGLIS technique and in particular the novel in-gas-jet laser ionization and spectroscopy method. The layout of the laboratory, the gascell chamber design, laser system and gas-jet formation simulations and tests have been discussed in recent publications [10,14]. The radio-frequency quadrupole (RFQ) ion guides, discussed in this contribution, form part of the IGLIS setup.…”

“…The in-gasjet laser ionization spectroscopy method can combine the high efficiency of conventional in-source technique, with the improved spectral resolution by at least an order of magnitude [11][12][13]. When the jet is formed under nonoptimal conditions, however, this can have adverse effects on the gas-jet conditions and therefore also on the laserspectroscopic resolution [14]. Using the stopping and fast extraction by a purified noble gas, isotopes with half-lives above 100 ms and produced at a rate of only 1 atom every 10 s are expected to be measured with a spectral resolution of δν/ν ≈ 1 × 10 7 (≈ 100 MHz) [12].…”