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Title: Lifetime of the metastable 2/sup 3/S/sub 1/ state in stored Li/sup +/ ions

Abstract

A laser-induced fluorescence technique combined with the observation of spontaneous magnetic dipole photons from the highly metastable 2/sup 3/S/sub 1/ state of Li/sup +/ was used to measure the radiative lifetime of this state. The ions are created by electron impact on a lithium atomic beam and are subsequently stored for periods of many seconds in an RF-quadrupole ion trap. A tunable dye laser excites the 2/sup 3/S--2/sup 3/P, transition at 5485A, and the intercombination electric dipole transition 2/sup 3/P/sub 1/--1 /sup 1/S/sub 0/ at 202A is observed. This process depletes the metastable population in a time tau/sub d/ < 1 sec < < tau/sub /sup 3/S/sub 1// and provides a measure of the total number of metastables. Comparison with the rate of 210A spontaneously emitted photons yields a measured value for the 2/sup 3/S/sub 1/ radiative lifetime of tau/sub rad/ = 58.6 +- 12.9 sec, where the quoted error represents 95% confidence levels. The theoretical lifetime is tau/sub theory/ = 49.0 sec. The measured value includes data taken with both /sup 6/Li/sup +/ and /sup 7/Li/sup +/ isotopes and was corrected for the slightly different detector efficiencies at 202A and 210A. A careful study of nonradiative quenching of themore » metastable state was necessary to understand observed differences between tau/sub rad/ and tau/sub /sup 3/S/sub 1//, the total metastable lifetime. Spatial density profiles of the ions within the trap, useful for determining the ion temperature, were obtained by scanning the laser beam horizontally across the ion trap while storing 2/sup 3/P/sub 1/--/sup 1/S/sub 0/ photon counts as a function of the laser beam's position. Agreement with a simple equilibrium model, including space charge effects, is satisfactory. A study of the optical pumping process is necessary to understand the laser-ion interaction, and observational and theoretical data are presented. 47 references.« less

Authors:
Publication Date:
Research Org.:
California Univ., Berkeley (USA). Lawrence Berkeley Lab.
OSTI Identifier:
6129453
Report Number(s):
LBL-9082
TRN: 79-017224
DOE Contract Number:  
W-7405-ENG-48
Resource Type:
Technical Report
Resource Relation:
Other Information: Thesis
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; LITHIUM IONS; METASTABLE STATES; CATIONS; DATA COVARIANCES; DIPOLES; EXPERIMENTAL DATA; GRAPHS; ISOLATED VALUES; LIFETIME; LITHIUM 6; LITHIUM 7; PHOTONS; POLARIZATION; ALKALI METAL ISOTOPES; ATOMIC IONS; CHARGED PARTICLES; DATA; DATA FORMS; ELEMENTARY PARTICLES; ENERGY LEVELS; EXCITED STATES; INFORMATION; IONS; ISOTOPES; LIGHT NUCLEI; LITHIUM ISOTOPES; MASSLESS PARTICLES; MULTIPOLES; NUCLEI; NUMERICAL DATA; ODD-EVEN NUCLEI; ODD-ODD NUCLEI; STABLE ISOTOPES; 640302* - Atomic, Molecular & Chemical Physics- Atomic & Molecular Properties & Theory

Citation Formats

Knight, R.D. Lifetime of the metastable 2/sup 3/S/sub 1/ state in stored Li/sup +/ ions. United States: N. p., 1979. Web. doi:10.2172/6129453.
Knight, R.D. Lifetime of the metastable 2/sup 3/S/sub 1/ state in stored Li/sup +/ ions. United States. doi:10.2172/6129453.
Knight, R.D. Sun . "Lifetime of the metastable 2/sup 3/S/sub 1/ state in stored Li/sup +/ ions". United States. doi:10.2172/6129453. https://www.osti.gov/servlets/purl/6129453.
@article{osti_6129453,
title = {Lifetime of the metastable 2/sup 3/S/sub 1/ state in stored Li/sup +/ ions},
author = {Knight, R.D.},
abstractNote = {A laser-induced fluorescence technique combined with the observation of spontaneous magnetic dipole photons from the highly metastable 2/sup 3/S/sub 1/ state of Li/sup +/ was used to measure the radiative lifetime of this state. The ions are created by electron impact on a lithium atomic beam and are subsequently stored for periods of many seconds in an RF-quadrupole ion trap. A tunable dye laser excites the 2/sup 3/S--2/sup 3/P, transition at 5485A, and the intercombination electric dipole transition 2/sup 3/P/sub 1/--1 /sup 1/S/sub 0/ at 202A is observed. This process depletes the metastable population in a time tau/sub d/ < 1 sec < < tau/sub /sup 3/S/sub 1// and provides a measure of the total number of metastables. Comparison with the rate of 210A spontaneously emitted photons yields a measured value for the 2/sup 3/S/sub 1/ radiative lifetime of tau/sub rad/ = 58.6 +- 12.9 sec, where the quoted error represents 95% confidence levels. The theoretical lifetime is tau/sub theory/ = 49.0 sec. The measured value includes data taken with both /sup 6/Li/sup +/ and /sup 7/Li/sup +/ isotopes and was corrected for the slightly different detector efficiencies at 202A and 210A. A careful study of nonradiative quenching of the metastable state was necessary to understand observed differences between tau/sub rad/ and tau/sub /sup 3/S/sub 1//, the total metastable lifetime. Spatial density profiles of the ions within the trap, useful for determining the ion temperature, were obtained by scanning the laser beam horizontally across the ion trap while storing 2/sup 3/P/sub 1/--/sup 1/S/sub 0/ photon counts as a function of the laser beam's position. Agreement with a simple equilibrium model, including space charge effects, is satisfactory. A study of the optical pumping process is necessary to understand the laser-ion interaction, and observational and theoretical data are presented. 47 references.},
doi = {10.2172/6129453},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1979},
month = {4}
}