Physical Review A

Lifetime and hyperfine structure of Li− excited states

Donald R. Beck, Cleanthes A. Nicolaides

Published Nov 1, 1983• 18 citations

Abstract

The newly discovered excited states of ${\mathrm{Li}}^{\ensuremath{-}}$ are examined from a many-body point of view. Our result for the $^{5}S^{o}$ lifetime includes the contribution of radiative autoionization. This removes one-third of the previous discrepancy between theory (our value = 2.7 ns) and experiment (= 2.3 ns). The first predictions of the hyperfine structures (hfs) of the ${\mathrm{Li}}^{\ensuremath{-}}$ $^{5}S^{o}$ and $^{5}P$ states are made, and the change in the hfs parameters as $p$ electrons are removed is studied.

DOI: 10.1103/physreva.28.3112

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Physical Review A

Lifetime and hyperfine structure of Li− excited states

Donald R. Beck, Cleanthes A. Nicolaides

Published Nov 1, 1983• 18 citations

Publisher

Abstract

The newly discovered excited states of

{\mathrm{Li}}^{\ensuremath{-}}

are examined from a many-body point of view. Our result for the

^{5}S^{o}

lifetime includes the contribution of radiative autoionization. This removes one-third of the previous discrepancy between theory (our value = 2.7 ns) and experiment (= 2.3 ns). The first predictions of the hyperfine structures (hfs) of the

{\mathrm{Li}}^{\ensuremath{-}}

^{5}S^{o}

and

^{5}P

states are made, and the change in the hfs parameters as

p

electrons are removed is studied.

DOI: 10.1103/physreva.28.3112

Related papers

Hyperfine structure effects in probing atomic alignment

I. M. Bell, C. J. K. Quayle, Keith R. Burnett

We have performed an analysis of the effect of hyperfine structure in an experiment in which an aligned excited state is probed using linearly polarized light. The state is born with a given electronic alignment resulting from a collisional process. It is probed after a time which is short in comparison to its radiative lifetime but much longer than ω−1hfs, where ℏωhfs is the hyperfine splitting. This means that hyperfine structure has ample time to ‘‘develop.’’ It is therefore essential to take into account both the hyperfine structure of the level and the manner in which the alignment is affected by recoupling to the new basis. Ratios of fluorescent intensities for different laser polarization configurations contain information on the alignment of the system. We show how these may be calculated for a system with several isotopes, some of which have hyperfine structure, and where many components are probed with appreciable strength. A comparison is made with our experimental results for the Hg(6 3P1) level probed on the 6 3P1–7 3S1 transition. The presence of hyperfine structure has a considerable influence on the measurements. It is important to understand such effects if one is to obtain information on the nascent electronic alignment by observation of the fluorescent intensities.We have performed an analysis of the effect of hyperfine structure in an experiment in which an aligned excited state is probed using linearly polarized light. The state is born with a given electronic alignment resulting from a collisional process. It is probed after a time which is short in comparison to its radiative lifetime but much longer than ω−1hfs, where ℏωhfs is the hyperfine splitting. This means that hyperfine structure has ample time to ‘‘develop.’’ It is therefore essential to take into account both the hyperfine structure of the level and the manner in which the alignment is affected by recoupling to the new basis. Ratios of fluorescent intensities for different laser polarization configurations contain information on the alignment of the system. We show how these may be calculated for a system with several isotopes, some of which have hyperfine structure, and where many components are probed with appreciable strength. A comparison is made with our experimental results for the Hg(6 3P1) level probed on the 6 3P1–7 3S1 transition. The presence of hyperfine structure has a considerable influence on the measurements. It is important to understand such effects if one is to obtain information on the nascent electronic alignment by observation of the fluorescent intensities.

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Lifetime, Coherence Narrowing, and Hyperfine Structure of the (6s26p7s) P1∘3 State in Lead

E. B. Saloman, W. Happer

The lifetime and hyperfine structure of the $(6{s}^{2}6p7s) ^{3}{P}_{1}^{\ensuremath{\circ}}$ excited state in lead have been investigated by the technique of level-crossing spectroscopy. The lifetime of the state was determined to be $\ensuremath{\tau}=5.75(20)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}$ sec. The linewidth of the level-crossing signal was observed to saturate at a "coherence-narrowed" value in agreement with theoretical predictions. The magnitude of this narrowing corresponds to a 27(3)% branching ratio to the ground state. When the branching ratio and the lifetime are combined with the $f(3639 \mathrm{\AA{}}):f(4058 \mathrm{\AA{}})$ oscillator-strength ratio measured by Khokhlov, one may infer the absolute $f$ values: $f(2833 \mathrm{\AA{}})=0.169(17)$ , $f(3639 \mathrm{\AA{}})=0.040(8)$ , $f(4058 \mathrm{\AA{}})=0.155(31)$ . The high-field level crossing in the hyperfine structure of the first $^{3}{P}_{1}^{\ensuremath{\circ}}$ state of ${\mathrm{Pb}}^{207}$ was found to occur at a magnetic field ${H}_{c}=4661.1(4)$ G, which corresponds to a magnetic-dipole-interaction constant $A=8.811(17)\ifmmode\times\else\texttimes\fi{}{10}^{9}$ cps.The lifetime and hyperfine structure of the $(6{s}^{2}6p7s) ^{3}{P}_{1}^{\ensuremath{\circ}}$ excited state in lead have been investigated by the technique of level-crossing spectroscopy. The lifetime of the state was determined to be $\ensuremath{\tau}=5.75(20)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}$ sec. The linewidth of the level-crossing signal was observed to saturate at a "coherence-narrowed" value in agreement with theoretical predictions. The magnitude of this narrowing corresponds to a 27(3)% branching ratio to the ground state. When the branching ratio and the lifetime are combined with the $f(3639 \mathrm{\AA{}}):f(4058 \mathrm{\AA{}})$ oscillator-strength ratio measured by Khokhlov, one may infer the absolute $f$ values: $f(2833 \mathrm{\AA{}})=0.169(17)$, $f(3639 \mathrm{\AA{}})=0.040(8)$, $f(4058 \mathrm{\AA{}})=0.155(31)$. The high-field level crossing in the hyperfine structure of the first $^{3}{P}_{1}^{\ensuremath{\circ}}$ state of ${\mathrm{Pb}}^{207}$ was found to occur at a magnetic field ${H}_{c}=4661.1(4)$ G, which corresponds to a magnetic-dipole-interaction constant $A=8.811(17)\ifmmode\times\else\texttimes\fi{}{10}^{9}$ cps.

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Fine and hyperfine structure of the Li− spectrum

K. T. Cheng, Jonathan E. Hardis, E. J. Dehm +1 more

The fine and hyperfine structures of the doubly excited, quintet states of the $^{7}\mathrm{Li}^{\ensuremath{-}}$ ion are of comparable magnitude. This leads to strong second-order hyperfine corrections and to significant distortion of the Land\'e interval rule. We discuss the results of our many-body calculations in this system, and also in the analogous lithium quartet systems for which experimental data exist. We find that the hyperfine matrix elements of these few-electron systems may be adequately computed without detailed consideration of the electron correlations. Fine structure is significantly affected by such correlations. Experimental verification of the ${\mathrm{Li}}^{\ensuremath{-}}$ structure is underway.The fine and hyperfine structures of the doubly excited, quintet states of the $^{7}\mathrm{Li}^{\ensuremath{-}}$ ion are of comparable magnitude. This leads to strong second-order hyperfine corrections and to significant distortion of the Land\'e interval rule. We discuss the results of our many-body calculations in this system, and also in the analogous lithium quartet systems for which experimental data exist. We find that the hyperfine matrix elements of these few-electron systems may be adequately computed without detailed consideration of the electron correlations. Fine structure is significantly affected by such correlations. Experimental verification of the ${\mathrm{Li}}^{\ensuremath{-}}$ structure is underway.

Physical Review AAug 1, 198414 citations

Precise determination of the 2P radiative atomic lifetime of lithium using photoassociative spectroscopy

W. I. McAlexander

Spectroscopy of the high-lying vibrational levels of the $1\\sp3\\Sigma\\sbsp{g}{+}$ and $1\\sp1\\Sigma\\sbsp{u}{+}$ states of both $\\rm\\sp6Li\\sb2$ and $\\rm\\sp7Li\\sb2$ has been accomplished via photoassociation of ultracold atomic lithium confined in a magneto-optical trap. Both these molecular states correlate to $2S\\sb{1/2}$ plus $2P\\sb{1/2}$ free atomic states. The long range part of these molecular potentials depends on the 2P atomic radiative lifetime. Accurate models were constructed for both the $1\\sp3\\Sigma\\sbsp{g}{+}$ and $1\\sp1\\Sigma\\sbsp{u}{+}$ potentials. By fitting these models to the experimentally measured vibrational levels observed in $\\rm\\sp6Li\\sb2$ and $\\rm\\sp7Li\\sb2$ , we have been able to extract a value for the 2P lifetime of lithium. Fitting to the absolute values of the data gives a value of 26.99 $\\pm$ 0.16 ns whereas fitting to differences in the spectral features gives a value of 27.04 $\\pm$ 0.18 ns. While both values agree with previous work, improvements made in the potential models would enable this analysis to resolve the current discrepancy between experiment and theory.Spectroscopy of the high-lying vibrational levels of the $1\\sp3\\Sigma\\sbsp{g}{+}$ and $1\\sp1\\Sigma\\sbsp{u}{+}$ states of both $\\rm\\sp6Li\\sb2$ and $\\rm\\sp7Li\\sb2$ has been accomplished via photoassociation of ultracold atomic lithium confined in a magneto-optical trap. Both these molecular states correlate to $2S\\sb{1/2}$ plus $2P\\sb{1/2}$ free atomic states. The long range part of these molecular potentials depends on the 2P atomic radiative lifetime. Accurate models were constructed for both the $1\\sp3\\Sigma\\sbsp{g}{+}$ and $1\\sp1\\Sigma\\sbsp{u}{+}$ potentials. By fitting these models to the experimentally measured vibrational levels observed in $\\rm\\sp6Li\\sb2$ and $\\rm\\sp7Li\\sb2$, we have been able to extract a value for the 2P lifetime of lithium. Fitting to the absolute values of the data gives a value of 26.99 $\\pm$ 0.16 ns whereas fitting to differences in the spectral features gives a value of 27.04 $\\pm$ 0.18 ns. While both values agree with previous work, improvements made in the potential models would enable this analysis to resolve the current discrepancy between experiment and theory.

Jan 1, 19950 citations

Observation of hyperfine structure and isotope shift in autoionizing states

R. J. de Graaff, Erwin A. J. M. Bente, W. Hogervorst +1 more

We report the first observation of hyperfine structure and isotope shift in autoionizing states. This structure was investigated in the $5{d}_{\frac{3}{2}}\mathrm{nf} J=4,5(n=36\ensuremath{-}40)$ barium Rydberg series, excited from the recently localized metastable $5{d}^{2}^{1}G_{4}$ level. An isotope-selective detection method was used in a cw laser spectroscopic experiment on a collimated atomic beam. The experimental data provide valuable additional information for the analyses of these doubly excited series.We report the first observation of hyperfine structure and isotope shift in autoionizing states. This structure was investigated in the $5{d}_{\frac{3}{2}}\mathrm{nf} J=4,5(n=36\ensuremath{-}40)$ barium Rydberg series, excited from the recently localized metastable $5{d}^{2}^{1}G_{4}$ level. An isotope-selective detection method was used in a cw laser spectroscopic experiment on a collimated atomic beam. The experimental data provide valuable additional information for the analyses of these doubly excited series.

Physical Review AJun 1, 19889 citations

Determination of the Fine and Hyperfine Structure and Lifetimes of the (1S2S2P) QUADRUPLET-P(0) Metastable Autoionizing States of LITHIUM-6 and LITHIUM-7.

Morris R. Levitt

Jan 1, 19680 citations

The newly discovered excited states of

{\mathrm{Li}}^{\ensuremath{-}}

are examined from a many-body point of view. Our result for the

^{5}S^{o}

{\mathrm{Li}}^{\ensuremath{-}}

^{5}S^{o}

and

^{5}P

states are made, and the change in the hfs parameters as

p

electrons are removed is studied.

f(3639 \mathrm{\AA{}}):f(4058 \mathrm{\AA{}})

oscillator-strength ratio measured by Khokhlov, one may infer the absolute

f

values:

f(2833 \mathrm{\AA{}})=0.169(17)

f(3639 \mathrm{\AA{}})=0.040(8)

f(4058 \mathrm{\AA{}})=0.155(31)

. The high-field level crossing in the hyperfine structure of the first $^{3}{P}_{1}^{\ensuremath{\circ}}$ state of

{\mathrm{Pb}}^{207}

was found to occur at a magnetic field

{H}_{c}=4661.1(4)

G, which corresponds to a magnetic-dipole-interaction constant $A=8.811(17)\ifmmode\times\else\texttimes\fi{}{10}^{9}$ cps.

Spectroscopy of the high-lying vibrational levels of the

1\\sp3\\Sigma\\sbsp{g}{+}

and

1\\sp1\\Sigma\\sbsp{u}{+}

states of both

\\rm\\sp6Li\\sb2

and

\\rm\\sp7Li\\sb2

has been accomplished via photoassociation of ultracold atomic lithium confined in a magneto-optical trap. Both these molecular states correlate to

2S\\sb{1/2}

plus

2P\\sb{1/2}

free atomic states. The long range part of these molecular potentials depends on the 2P atomic radiative lifetime. Accurate models were constructed for both the

1\\sp3\\Sigma\\sbsp{g}{+}

and

1\\sp1\\Sigma\\sbsp{u}{+}

potentials. By fitting these models to the experimentally measured vibrational levels observed in

\\rm\\sp6Li\\sb2

and

\\rm\\sp7Li\\sb2

, we have been able to extract a value for the 2P lifetime of lithium. Fitting to the absolute values of the data gives a value of 26.99

\\pm

0.16 ns whereas fitting to differences in the spectral features gives a value of 27.04

\\pm

0.18 ns. While both values agree with previous work, improvements made in the potential models would enable this analysis to resolve the current discrepancy between experiment and theory.