Applied Optics

An Apparatus for the Precise Determination of Lifetimes of Atomic States

E. E. Habib, B P Kibble, G. H. Copley

Published Apr 1, 1968• 12 citations

Abstract

The time which elapses between excitation of an atom by a pulse of light and subsequent emission of radiation may be measured by a delayed coincidence technique. A system which is suitable for measuring lifetimes of atomic states in the range 10(-7)-10(-8) sec, employing a high speed Kerr shutter in conjunction with a time-to-pulse height converter and kicksorter, is described.

DOI: 10.1364/ao.7.000673

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Applied Optics

An Apparatus for the Precise Determination of Lifetimes of Atomic States

E. E. Habib, B P Kibble, G. H. Copley

Published Apr 1, 1968• 12 citations

Publisher

Abstract

DOI: 10.1364/ao.7.000673

Related papers

Measurements of Lifetimes of Excited States of Atoms by the Method of Delayed Coincidences

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NatureSep 1, 195422 citations

Inelastic Collisions between Excited Alkali Atoms and Molecules. II. The Quenching of Sodium Resonance Radiation by N2 , H2 , HD, and D2

B P Kibble, G. H. Copley, L. Krause

The cross sections for quenching collisions between excited sodium atoms and ${\mathrm{N}}_{2}$ , ${\mathrm{H}}_{2}$ , HD, and ${\mathrm{D}}_{2}$ molecules in their electronic ground states have been determined using a delayed-coincidence method. The sodium atoms in mixtures with the gases were excited with 20-nsec pulses of NaD radiation, and the delays between the exciting and fluorescent pulses were measured with a time-to-pulse-height converter. The resulting pulse-height spectra, which were accummulated in a 400-channel kicksorter, yielded the effective lifetimes ${\ensuremath{\tau}}^{\ensuremath{'}}$ of the sodium resonance state, which are shorter than the natural lifetime $\ensuremath{\tau}$ because of the nonradiative decay induced in collisions with the molecules. The cross sections for collisions with ${\mathrm{N}}_{2}$ , ${\mathrm{H}}_{2}$ , HD, and ${\mathrm{D}}_{2}$ , obtained from an analysis of the dependence of ${\ensuremath{\tau}}^{\ensuremath{'}}$ on the gas pressures, are 30.4\ifmmode\pm\else\textpm\fi{}1.2, 16.2\ifmmode\pm\else\textpm\fi{}0.3, 11.6\ifmmode\pm\else\textpm\fi{}0.4, and 9.8\ifmmode\pm\else\textpm\fi{}0.3 ${\mathrm{\AA{}}}^{2}$ , respectively.The cross sections for quenching collisions between excited sodium atoms and ${\mathrm{N}}_{2}$, ${\mathrm{H}}_{2}$, HD, and ${\mathrm{D}}_{2}$ molecules in their electronic ground states have been determined using a delayed-coincidence method. The sodium atoms in mixtures with the gases were excited with 20-nsec pulses of NaD radiation, and the delays between the exciting and fluorescent pulses were measured with a time-to-pulse-height converter. The resulting pulse-height spectra, which were accummulated in a 400-channel kicksorter, yielded the effective lifetimes ${\ensuremath{\tau}}^{\ensuremath{'}}$ of the sodium resonance state, which are shorter than the natural lifetime $\ensuremath{\tau}$ because of the nonradiative decay induced in collisions with the molecules. The cross sections for collisions with ${\mathrm{N}}_{2}$, ${\mathrm{H}}_{2}$, HD, and ${\mathrm{D}}_{2}$, obtained from an analysis of the dependence of ${\ensuremath{\tau}}^{\ensuremath{'}}$ on the gas pressures, are 30.4\ifmmode\pm\else\textpm\fi{}1.2, 16.2\ifmmode\pm\else\textpm\fi{}0.3, 11.6\ifmmode\pm\else\textpm\fi{}0.4, and 9.8\ifmmode\pm\else\textpm\fi{}0.3 ${\mathrm{\AA{}}}^{2}$, respectively.

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Effect of Imprisonment of Radiation in Sodium Vapor on the Measured Lifetime of the 3 P2 States

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The effect of imprisonment of radiation in sodium vapor on the measured lifetime of the $3 ^{2}P$ states has been investigated in an experiment in which the atoms in the vapor were excited with 10-nsec pulses of resonance radiation and the elapsed times between the exciting and the fluorescent pulses were recorded using a time-to-amplitude converter and kicksorter. At vapor densities below ${10}^{10}$ atoms/ ${\mathrm{cm}}^{3}$ , where there is no multiple scattering, the measured lifetime reaches a constant value of (1.63\ifmmode\pm\else\textpm\fi{}0.04)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ sec, equal to the natural lifetime of the $3 ^{2}P$ states. In the density range ${10}^{9}$ - ${10}^{13}$ atoms/ ${\mathrm{cm}}^{3}$ , the variation of the effective lifetime with the vapor density is in good agreement with the predictions of Milne's theory of radiation trapping; agreement with Holstein's theory is observed only in the range ${10}^{12}$ - ${10}^{13}$ atoms/ ${\mathrm{cm}}^{3}$ . The results of a subsidiary Hanle experiment show that a multiply scattered photon of sodium resonance fluorescence loses its original polarization and that, at high sodium vapor pressure, coherence is not preserved.The effect of imprisonment of radiation in sodium vapor on the measured lifetime of the $3 ^{2}P$ states has been investigated in an experiment in which the atoms in the vapor were excited with 10-nsec pulses of resonance radiation and the elapsed times between the exciting and the fluorescent pulses were recorded using a time-to-amplitude converter and kicksorter. At vapor densities below ${10}^{10}$ atoms/${\mathrm{cm}}^{3}$, where there is no multiple scattering, the measured lifetime reaches a constant value of (1.63\ifmmode\pm\else\textpm\fi{}0.04)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ sec, equal to the natural lifetime of the $3 ^{2}P$ states. In the density range ${10}^{9}$-${10}^{13}$ atoms/${\mathrm{cm}}^{3}$, the variation of the effective lifetime with the vapor density is in good agreement with the predictions of Milne's theory of radiation trapping; agreement with Holstein's theory is observed only in the range ${10}^{12}$-${10}^{13}$ atoms/${\mathrm{cm}}^{3}$. The results of a subsidiary Hanle experiment show that a multiply scattered photon of sodium resonance fluorescence loses its original polarization and that, at high sodium vapor pressure, coherence is not preserved.

Physical ReviewJan 5, 1967114 citations

Roy Edward Mitchell

A new high-efficiency photon-photon delayed coincidence lifetime measuring apparatus has been constructed and was used to study the 5d {dollar}\\sp4{dollar}F{dollar}\\sb{lcub}9/2{rcub}{dollar} {dollar}\\longrightarrow{dollar} 5p {dollar}\\sp4{dollar}D{dollar}\\sbsp{lcub}7/2{rcub}{lcub}\\rm o{rcub}{dollar} {dollar}\\longrightarrow{dollar} 5s {dollar}\\sp4{dollar}P{dollar}\\sb{lcub}5/2{rcub}{dollar} cascade in Kr II and the 6d {dollar}\\sp4{dollar}F{dollar}\\sb{lcub}7/2{rcub}{dollar} {dollar}\\longrightarrow{dollar} 6p {dollar}\\sp4{dollar}D{dollar}\\sbsp{lcub}5/2{rcub}{lcub}\\rm o{rcub}{dollar} {dollar}\\longrightarrow{dollar} 6s {dollar}\\sp4{dollar}P{dollar}\\sb{lcub}3/2{rcub}{dollar} cascade in Xe II. A neutral atomic beam was excited and ionized by electron impact, and the spontaneously emitted photons were collected by an ellipsoidal mirror, collimated by an aspheric lens, and detected by two Amperex XP2020Q fast linear-focussed photomultipliers provided with narrow-band interference filters. The spectrum of time delays was acquired by a time-to-amplitude converter-multichannel pulse-height analyser combination. The lifetime of the Kr II 5p {dollar}\\sp4{dollar}D{dollar}\\sbsp{lcub}7/2{rcub}{lcub}\\rm o{rcub}{dollar} state was found to be 7.004 {dollar}\\pm{dollar} 0.053 nanoseconds and is in agreement with two previous measurements. This first measurement provided a calibration of the newly constructed apparatus. It also has provided an improvement in the precision with which this lifetime is known by a factor of 3. The Xe II 6p {dollar}\\sp4{dollar}D{dollar}\\sbsp{lcub}5/2{rcub}{lcub}\\rm o{rcub}{dollar} state lifetime was found to be 9.634 {dollar}\\pm{dollar} 0.067 nanoseconds. This result agrees with several measurements of lower accuracy but does not agree with two previous measurements claiming high precision. This discrepancy has not been resolved in this work.A new high-efficiency photon-photon delayed coincidence lifetime measuring apparatus has been constructed and was used to study the 5d {dollar}\\sp4{dollar}F{dollar}\\sb{lcub}9/2{rcub}{dollar} {dollar}\\longrightarrow{dollar} 5p {dollar}\\sp4{dollar}D{dollar}\\sbsp{lcub}7/2{rcub}{lcub}\\rm o{rcub}{dollar} {dollar}\\longrightarrow{dollar} 5s {dollar}\\sp4{dollar}P{dollar}\\sb{lcub}5/2{rcub}{dollar} cascade in Kr II and the 6d {dollar}\\sp4{dollar}F{dollar}\\sb{lcub}7/2{rcub}{dollar} {dollar}\\longrightarrow{dollar} 6p {dollar}\\sp4{dollar}D{dollar}\\sbsp{lcub}5/2{rcub}{lcub}\\rm o{rcub}{dollar} {dollar}\\longrightarrow{dollar} 6s {dollar}\\sp4{dollar}P{dollar}\\sb{lcub}3/2{rcub}{dollar} cascade in Xe II. A neutral atomic beam was excited and ionized by electron impact, and the spontaneously emitted photons were collected by an ellipsoidal mirror, collimated by an aspheric lens, and detected by two Amperex XP2020Q fast linear-focussed photomultipliers provided with narrow-band interference filters. The spectrum of time delays was acquired by a time-to-amplitude converter-multichannel pulse-height analyser combination. The lifetime of the Kr II 5p {dollar}\\sp4{dollar}D{dollar}\\sbsp{lcub}7/2{rcub}{lcub}\\rm o{rcub}{dollar} state was found to be 7.004 {dollar}\\pm{dollar} 0.053 nanoseconds and is in agreement with two previous measurements. This first measurement provided a calibration of the newly constructed apparatus. It also has provided an improvement in the precision with which this lifetime is known by a factor of 3. The Xe II 6p {dollar}\\sp4{dollar}D{dollar}\\sbsp{lcub}5/2{rcub}{lcub}\\rm o{rcub}{dollar} state lifetime was found to be 9.634 {dollar}\\pm{dollar} 0.067 nanoseconds. This result agrees with several measurements of lower accuracy but does not agree with two previous measurements claiming high precision. This discrepancy has not been resolved in this work.

Jan 1, 19900 citations

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A. M. Dumont

Nov 1, 19760 citations

The cross sections for quenching collisions between excited sodium atoms and

{\mathrm{N}}_{2}

{\mathrm{H}}_{2}

, HD, and

{\mathrm{D}}_{2}

molecules in their electronic ground states have been determined using a delayed-coincidence method. The sodium atoms in mixtures with the gases were excited with 20-nsec pulses of NaD radiation, and the delays between the exciting and fluorescent pulses were measured with a time-to-pulse-height converter. The resulting pulse-height spectra, which were accummulated in a 400-channel kicksorter, yielded the effective lifetimes ${\ensuremath{\tau}}^{\ensuremath{'}}$ of the sodium resonance state, which are shorter than the natural lifetime $\ensuremath{\tau}$ because of the nonradiative decay induced in collisions with the molecules. The cross sections for collisions with

{\mathrm{N}}_{2}

{\mathrm{H}}_{2}

, HD, and

{\mathrm{D}}_{2}

, obtained from an analysis of the dependence of ${\ensuremath{\tau}}^{\ensuremath{'}}$ on the gas pressures, are 30.4\ifmmode\pm\else\textpm\fi{}1.2, 16.2\ifmmode\pm\else\textpm\fi{}0.3, 11.6\ifmmode\pm\else\textpm\fi{}0.4, and 9.8\ifmmode\pm\else\textpm\fi{}0.3

{\mathrm{\AA{}}}^{2}

, respectively.

The effect of imprisonment of radiation in sodium vapor on the measured lifetime of the

3 ^{2}P

states has been investigated in an experiment in which the atoms in the vapor were excited with 10-nsec pulses of resonance radiation and the elapsed times between the exciting and the fluorescent pulses were recorded using a time-to-amplitude converter and kicksorter. At vapor densities below

{10}^{10}

atoms/

{\mathrm{cm}}^{3}

, where there is no multiple scattering, the measured lifetime reaches a constant value of (1.63\ifmmode\pm\else\textpm\fi{}0.04)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}8}$ sec, equal to the natural lifetime of the

3 ^{2}P

states. In the density range

{10}^{9}

{10}^{13}

atoms/

{\mathrm{cm}}^{3}

, the variation of the effective lifetime with the vapor density is in good agreement with the predictions of Milne's theory of radiation trapping; agreement with Holstein's theory is observed only in the range

{10}^{12}

{10}^{13}

atoms/

{\mathrm{cm}}^{3}

. The results of a subsidiary Hanle experiment show that a multiply scattered photon of sodium resonance fluorescence loses its original polarization and that, at high sodium vapor pressure, coherence is not preserved.