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Title: A thermal beam of metastable krypton atoms produced by optical excitation.

Abstract

A room-temperature beam of krypton atoms in the metastable 5s[3/2]{sub 2} level is demonstrated via an optical excitation method. A Kr-discharge lamp is used to produce vacuum ultraviolet photons at 124 nm for the first-step excitation from the ground level 4p{sup 6} {sup 1}S{sub 0} to the 5s[3/2]{sub 1} level. An 819 nm Ti:sapphire laser is used for the second-step excitation from 5s[3/2]{sub 1} to 5s[3/2]{sub 2} followed by a spontaneous decay to the 5s[3/2]{sub 2} metastable level. A metastable atomic beam with an angular flux density of 3 x 10{sup 14} s{sup -1} sr{sup -1} is achieved at the total gas flow rate of 0.01 cm{sup 3}/s at STP (or 3 x 10{sup 17} at./s). The dependences of the flux on the gas flow rate, laser power, and lamp parameters are investigated.

Authors:
; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
944032
Report Number(s):
ANL/PHY/JA-57500
Journal ID: ISSN 0034-6748; RSINAK; TRN: US0900504
DOE Contract Number:
DE-AC02-06CH11357
Resource Type:
Journal Article
Resource Relation:
Journal Name: Rev. Sci. Instrum.; Journal Volume: 78; Journal Issue: Feb. 8, 2007
Country of Publication:
United States
Language:
ENGLISH
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ATOMIC BEAMS; ATOMS; DECAY; EXCITATION; FLUX DENSITY; GAS FLOW; GROUND LEVEL; KRYPTON; LASERS; LIGHT BULBS; PHOTONS

Citation Formats

Ding, Y., Hu, S.-M., Bailey, K., Davis, A. M., Dunford, R. W., Lu, Z.-T., O'Connor, T. P., Young, L., Univ. of Chicago, and Univ. of Science and Technology of China. A thermal beam of metastable krypton atoms produced by optical excitation.. United States: N. p., 2007. Web. doi:10.1063/1.2437193.
Ding, Y., Hu, S.-M., Bailey, K., Davis, A. M., Dunford, R. W., Lu, Z.-T., O'Connor, T. P., Young, L., Univ. of Chicago, & Univ. of Science and Technology of China. A thermal beam of metastable krypton atoms produced by optical excitation.. United States. doi:10.1063/1.2437193.
Ding, Y., Hu, S.-M., Bailey, K., Davis, A. M., Dunford, R. W., Lu, Z.-T., O'Connor, T. P., Young, L., Univ. of Chicago, and Univ. of Science and Technology of China. Thu . "A thermal beam of metastable krypton atoms produced by optical excitation.". United States. doi:10.1063/1.2437193.
@article{osti_944032,
title = {A thermal beam of metastable krypton atoms produced by optical excitation.},
author = {Ding, Y. and Hu, S.-M. and Bailey, K. and Davis, A. M. and Dunford, R. W. and Lu, Z.-T. and O'Connor, T. P. and Young, L. and Univ. of Chicago and Univ. of Science and Technology of China},
abstractNote = {A room-temperature beam of krypton atoms in the metastable 5s[3/2]{sub 2} level is demonstrated via an optical excitation method. A Kr-discharge lamp is used to produce vacuum ultraviolet photons at 124 nm for the first-step excitation from the ground level 4p{sup 6} {sup 1}S{sub 0} to the 5s[3/2]{sub 1} level. An 819 nm Ti:sapphire laser is used for the second-step excitation from 5s[3/2]{sub 1} to 5s[3/2]{sub 2} followed by a spontaneous decay to the 5s[3/2]{sub 2} metastable level. A metastable atomic beam with an angular flux density of 3 x 10{sup 14} s{sup -1} sr{sup -1} is achieved at the total gas flow rate of 0.01 cm{sup 3}/s at STP (or 3 x 10{sup 17} at./s). The dependences of the flux on the gas flow rate, laser power, and lamp parameters are investigated.},
doi = {10.1063/1.2437193},
journal = {Rev. Sci. Instrum.},
number = Feb. 8, 2007,
volume = 78,
place = {United States},
year = {Thu Feb 08 00:00:00 EST 2007},
month = {Thu Feb 08 00:00:00 EST 2007}
}
  • A room-temperature beam of krypton atoms in the metastable 5s[3/2]{sub 2} level is demonstrated via an optical excitation method. A Kr-discharge lamp is used to produce vacuum ultraviolet photons at 124 nm for the first-step excitation from the ground level 4p{sup 6} {sup 1}S{sub 0} to the 5s[3/2]{sub 1} level. An 819 nm Ti:sapphire laser is used for the second-step excitation from 5s[3/2]{sub 1} to 5s[3/2]{sub 2} followed by a spontaneous decay to the 5s[3/2]{sub 2} metastable level. A metastable atomic beam with an angular flux density of 3x10{sup 14} s{sup -1} sr{sup -1} is achieved at the total gasmore » flow rate of 0.01 cm{sup 3}/s at STP (or 3x10{sup 17} at./s). The dependences of the flux on the gas flow rate, laser power, and lamp parameters are investigated.« less
  • A microwave-driven discharge is used to produce a thermal beam of metastable krypton atoms at the 5s[3/2]{sub 2} level with an angular flux density of 7 x 10{sup 14} s{sup -1} sr{sup -1}, while consuming 1 x 10{sup 17} krypton atoms/s. This source of atomic beam uses commercially available microwave parts, and has achieved comparable beam flux and excitation efficiency with a previously described source that employs a rf-driven discharge [C. Y. Chen et al., Rev. Sci. Instrum. 72, 271 (2001)].
  • A microwave-driven discharge is used to produce a thermal beam of metastable krypton atoms at the 5s[3/2]{sub 2} level with an angular flux density of 7x10{sup 14} s{sup -1} sr{sup -1}, while consuming 1x10{sup 17} krypton atoms/s. This source of atomic beam uses commercially available microwave parts, and has achieved comparable beam flux and excitation efficiency with a previously described source that employs a rf-driven discharge [C. Y. Chen et al., Rev. Sci. Instrum. 72, 271 (2001)].
  • A rf-driven discharge is used to produce a beam of metastable krypton atoms at the 5s(3/2){sub 2} level with an angular flux density of 4x10{sup 14}s{sup -1}sr{sup -1} and most probable velocity of 290 m/s, while consuming 7x10{sup 16} krypton atoms/s. When operated in a gas-recirculation mode, the source consumes 2x10{sup 15} krypton atoms/s with the same atomic-beam output.
  • An apparatus for measuring absolute cross sections due to electron-impact excitation out of the metastable levels of rare-gas atoms via the optical method is described with the focus specifically on excitation out of the 2{sup 3}{ital S} metastable helium level. The metastable helium target (He{asterisk}) is prepared by charge exchange between 1.6 keV He{sup +} ions and cesium vapor. An electron beam crosses the fast metastable beam target at a right angle and the fluorescence is collected at right angles to both beams. The charge transfer reaction produces He atoms mainly in the {ital n}=2 He levels. Because the targetmore » contains a negligible ground state He fraction, we can measure excitation cross sections from excitation threshold up to an arbitrarily high energy (keV regime) which represents a major improvement over previous metastable excitation cross sections measurements. The He{asterisk} target density is extremely small ({approximately}10{sup 6} atoms/cm{sup 3}) yielding minuscule signal rates. We describe steps taken to maximize the signal-to-noise ratio. We discuss the implications of using a fast beam target including both the finite flight time of the excited atoms across the light gathering region and the reduction of the cascade contributions to the apparent cross sections. A discussion of the identification and elimination of various systematic effects is also given. To measure absolute cross sections, we explicitly determine the spatial distributions of both the electron and metastable beams, as well as the spatially dependent response of the fluorescence gathering region. We determine the absolute flux of fast metastable atoms using a thermal detector calibrated with a He{sup +} ion beam. As examples, we present absolute cross sections for excitation out of the 2{sup 3}{ital S} metastable level into the 3{sup 3}{ital D} and 4{sup 3}{ital D} levels. {copyright} {ital 1996 American Institute of Physics.}« less