Physical Review A

Lifetimes of n P2 states of thallium by analysis of cascade fluorescence following two-photon excitation

John V. James, Charles C. Wang, Curtis Doty

Published Aug 1, 1986• 14 citations

Abstract

The lifetimes of the n ${\mathrm{}}^{2}$${P}_{1/2}$ and n ${\mathrm{}}^{2}$${P}_{3/2}$ states of thallium, n=7--11, have been determined through measurements of the fluorescence signal resulting from two-photon excitation in an atomic beam. The temporal dependence of the fluorescence signal is determined by solving the equations governing cascade spontaneous fluorescence from higher-lying initial states. It is shown that under conditions applicable to our experiments, the asymptotic decay of the fluorescence is a measure of the lifetime of the initial state. The possibility of self-absorption of the fluorescence within the atomic beam is investigated; it is found to be negligible over the range of thallium densities used in the experiment. Our lifetime measurements for these eight $^{2}\mathrm{P}$ states are compared with other known experimental data and with the results of previous semiempirical calculations.

DOI: 10.1103/physreva.34.1117

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Two-photon Resonant Excitation Of Thallium In An Atomic Beam (multiphoton, Radiative Lifetimes).

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Jan 1, 19860 citations

Measurements of the lifetimes of the 7 2 P1/2o and 7 2 P3/2o excited states of thallium

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Lifetime of the 2P11 and 3P11 States of Atomic Helium

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Physical Review AJan 1, 197121 citations

Physical Review A

Lifetimes of n P2 states of thallium by analysis of cascade fluorescence following two-photon excitation

John V. James, Charles C. Wang, Curtis Doty

Published Aug 1, 1986• 14 citations

Publisher

Abstract

The lifetimes of the n

{\mathrm{}}^{2}$${P}_{1/2}

and n

{\mathrm{}}^{2}$${P}_{3/2}

states of thallium, n=7--11, have been determined through measurements of the fluorescence signal resulting from two-photon excitation in an atomic beam. The temporal dependence of the fluorescence signal is determined by solving the equations governing cascade spontaneous fluorescence from higher-lying initial states. It is shown that under conditions applicable to our experiments, the asymptotic decay of the fluorescence is a measure of the lifetime of the initial state. The possibility of self-absorption of the fluorescence within the atomic beam is investigated; it is found to be negligible over the range of thallium densities used in the experiment. Our lifetime measurements for these eight

^{2}\mathrm{P}

states are compared with other known experimental data and with the results of previous semiempirical calculations.

DOI: 10.1103/physreva.34.1117

Related papers

Two-photon Resonant Excitation Of Thallium In An Atomic Beam (multiphoton, Radiative Lifetimes).

John V. James

We have observed fluorescence and ionization signals resulting from two-photon resonant excitation of thallium in an atomic beam. The output of a pulsed dye laser is used to excite the resonance between the ground state (6('2)P(,1/2)) and an excited n('2)P state of thallium. Both two-photon absorption and three-photon absorption occur simultaneously; the latter results in photoionization of the atom. The excited states populated by two-photon absorption decay via cascade fluorescence back to the ground state; one or more of these spectral components constitute our fluorescence signal. The lifetimes of the excited n('2)P states of thallium have been measured directly by observing the exponential decay of this fluorescence. Calculations are included to ascertain the time required for the fluorescence signal to reach within 2% of a simple exponential decay. This decay is a measure of the lifetime of the initial state, under the condition that none of the fluorescence components arise from states which are populated by cascade through longer-lived states. The lifetimes of the n('2)P(,1/2) and n('2)P(,3/2) states of thallium for n = 7 to 11 are determined in this manner and compared with the values deduced from semi-empirical calculations of oscillator strengths by various authors. For calculations employing the effects of core polarizability in the electron wavefunctions and in the transition matrix elements, the agreement is very good--to within our experimental uncertainty, which is typically(, )<5%. Our measurements are also compared to the four other known experimental values for such excited states of thallium. Some of these previous experiments and calculations were carried out in conjunction with parity non-conservation experiments in thallium. Our measurements may provide useful checks on the accuracy of some of the calculations performed in the evaluation of such experiments. The ionization and fluorescence signals are also studied under conditions of strong saturation of the two-photon resonance with the 7('2)P states. The manifestation of saturation in the ionization signal is a broadening of the excitation spectrum, which is found to greatly exceed that of the fluorescence signal. Furthermore, the ratio of the ionization signal to the fluorescence signal at the peak of the resonance is found to vary linearly at intensities below about 10('9) W/cm('2); this too saturates at higher intensities. Various models are employed to simulate the observed behavior, encompassing both rate equations as well as density matrix formulations. The numerical solutions to these models are compared with the observed behavior; the agreement is found to depend strongly on the assumed experi- mental conditions to which the ensemble of atoms is subjected.We have observed fluorescence and ionization signals resulting from two-photon resonant excitation of thallium in an atomic beam. The output of a pulsed dye laser is used to excite the resonance between the ground state (6('2)P(,1/2)) and an excited n('2)P state of thallium. Both two-photon absorption and three-photon absorption occur simultaneously; the latter results in photoionization of the atom. The excited states populated by two-photon absorption decay via cascade fluorescence back to the ground state; one or more of these spectral components constitute our fluorescence signal. The lifetimes of the excited n('2)P states of thallium have been measured directly by observing the exponential decay of this fluorescence. Calculations are included to ascertain the time required for the fluorescence signal to reach within 2% of a simple exponential decay. This decay is a measure of the lifetime of the initial state, under the condition that none of the fluorescence components arise from states which are populated by cascade through longer-lived states. The lifetimes of the n('2)P(,1/2) and n('2)P(,3/2) states of thallium for n = 7 to 11 are determined in this manner and compared with the values deduced from semi-empirical calculations of oscillator strengths by various authors. For calculations employing the effects of core polarizability in the electron wavefunctions and in the transition matrix elements, the agreement is very good--to within our experimental uncertainty, which is typically(, )<5%. Our measurements are also compared to the four other known experimental values for such excited states of thallium. Some of these previous experiments and calculations were carried out in conjunction with parity non-conservation experiments in thallium. Our measurements may provide useful checks on the accuracy of some of the calculations performed in the evaluation of such experiments. The ionization and fluorescence signals are also studied under conditions of strong saturation of the two-photon resonance with the 7('2)P states. The manifestation of saturation in the ionization signal is a broadening of the excitation spectrum, which is found to greatly exceed that of the fluorescence signal. Furthermore, the ratio of the ionization signal to the fluorescence signal at the peak of the resonance is found to vary linearly at intensities below about 10('9) W/cm('2); this too saturates at higher intensities. Various models are employed to simulate the observed behavior, encompassing both rate equations as well as density matrix formulations. The numerical solutions to these models are compared with the observed behavior; the agreement is found to depend strongly on the assumed experi- mental conditions to which the ensemble of atoms is subjected.

Jan 1, 19860 citations

Measurements of the lifetimes of the 7 2 P1/2o and 7 2 P3/2o excited states of thallium

John V. James, Charles C. Wang, Chuan Guo

The lifetimes of the 7 ${\mathrm{}}^{2}$ ${P}_{1/2}^{o}$ and 7 ${\mathrm{}}^{2}$ ${P}_{3/2}^{o}$ states of thallium have been measured for the first time by observing the fluorescence decay following two-photon resonant excitation in an atomic beam. The values obtained for these states are 61.9 and 48.4 ns, respectively, with an uncertainty of 2%. These results are in good quantitative agreement with the calculations of Bardsley and Norcross, which include the effect of core polarizability.The lifetimes of the 7 ${\mathrm{}}^{2}$${P}_{1/2}^{o}$ and 7 ${\mathrm{}}^{2}$${P}_{3/2}^{o}$ states of thallium have been measured for the first time by observing the fluorescence decay following two-photon resonant excitation in an atomic beam. The values obtained for these states are 61.9 and 48.4 ns, respectively, with an uncertainty of 2%. These results are in good quantitative agreement with the calculations of Bardsley and Norcross, which include the effect of core polarizability.

Physical Review AJul 1, 19859 citations

Fast-beam laser lifetime measurements of the cesium 6p2P1/2,3/2 states

Robert J. Rafac, Carol E. Tanner, A. E. Livingston +1 more

We provide a detailed description of our fast-beam laser lifetime measurements in atomic cesium. Selective excitation of the neutral ${}^{133}\mathrm{Cs}$ $6p{}^{2}{P}_{1/2}$ and $6p{}^{2}{P}_{3/2}$ states is accomplished with resonant diode laser light directed transversely to the atomic velocity. The in-flight decay of the excited-state fluorescence is observed with a position-correlated single photon-counting detector. The Doppler-shifted $6p{}^{2}{P}_{3/2}$ resonance, when probed with longitudinally propagating laser radiation, provides a precise means for determination of the beam velocity, and converts the position scale to a time scale. Our lifetime results are $35.07\ifmmode\pm\else\textpm\fi{}0.10 \mathrm{ns}$ for the $6p{}^{2}{P}_{1/2}$ state and $30.57\ifmmode\pm\else\textpm\fi{}0.07 \mathrm{ns}$ for the $6p{}^{2}{P}_{3/2}$ state. These results represent a data set larger than in our previous work, and include beam divergence corrections which have been evaluated by two different methods. We present comparisons of our results with previous measurements and with relativistic many-body calculations of atomic transition matrix elements in this neutral alkali system.We provide a detailed description of our fast-beam laser lifetime measurements in atomic cesium. Selective excitation of the neutral ${}^{133}\mathrm{Cs}$ $6p{}^{2}{P}_{1/2}$ and $6p{}^{2}{P}_{3/2}$ states is accomplished with resonant diode laser light directed transversely to the atomic velocity. The in-flight decay of the excited-state fluorescence is observed with a position-correlated single photon-counting detector. The Doppler-shifted $6p{}^{2}{P}_{3/2}$ resonance, when probed with longitudinally propagating laser radiation, provides a precise means for determination of the beam velocity, and converts the position scale to a time scale. Our lifetime results are $35.07\ifmmode\pm\else\textpm\fi{}0.10 \mathrm{ns}$ for the $6p{}^{2}{P}_{1/2}$ state and $30.57\ifmmode\pm\else\textpm\fi{}0.07 \mathrm{ns}$ for the $6p{}^{2}{P}_{3/2}$ state. These results represent a data set larger than in our previous work, and include beam divergence corrections which have been evaluated by two different methods. We present comparisons of our results with previous measurements and with relativistic many-body calculations of atomic transition matrix elements in this neutral alkali system.

Physical Review ANov 1, 199992 citations

Lifetime measurements of the 7p levels of atomic francium

J. E. Simsarian, Luis A. Orozco, Gene D. Sprouse +1 more

We present lifetime measurements of the ${7p}^{2}{P}_{3/2}$ and ${7p}^{2}{P}_{1/2}$ levels of Fr. We use a time-correlated single-photon counting technique on a cold sample of ${}^{210}\mathrm{Fr}$ atoms in a magneto-optic trap. We excite the atoms with the trapping and repumping beams of the magneto-optic trap and detect the decay of the atomic fluorescence. The results are a precision experimental test of the atomic many-body perturbation theory applied to the heaviest alkali metal. The lifetime results are 21.02(11) ns and 29.45(11) ns for the ${7p}^{2}{P}_{3/2}$ and ${7p}^{2}{P}_{1/2}$ levels, respectively. This gives a line strength ratio ${\mathcal{S}}_{1/2}$ / ${\mathcal{S}}_{3/2}$ of 0.526(3) for these levels in Fr. To study sources of systematic errors we measure the lifetimes of ${5p}^{2}{P}_{3/2}$ and ${5p}^{2}{P}_{1/2}$ in stable ${}^{87}\mathrm{Rb}$ and obtain 26.20(9) ns and 27.64(4) ns, respectively.We present lifetime measurements of the ${7p}^{2}{P}_{3/2}$ and ${7p}^{2}{P}_{1/2}$ levels of Fr. We use a time-correlated single-photon counting technique on a cold sample of ${}^{210}\mathrm{Fr}$ atoms in a magneto-optic trap. We excite the atoms with the trapping and repumping beams of the magneto-optic trap and detect the decay of the atomic fluorescence. The results are a precision experimental test of the atomic many-body perturbation theory applied to the heaviest alkali metal. The lifetime results are 21.02(11) ns and 29.45(11) ns for the ${7p}^{2}{P}_{3/2}$ and ${7p}^{2}{P}_{1/2}$ levels, respectively. This gives a line strength ratio ${\mathcal{S}}_{1/2}$/${\mathcal{S}}_{3/2}$ of 0.526(3) for these levels in Fr. To study sources of systematic errors we measure the lifetimes of ${5p}^{2}{P}_{3/2}$ and ${5p}^{2}{P}_{1/2}$ in stable ${}^{87}\mathrm{Rb}$ and obtain 26.20(9) ns and 27.64(4) ns, respectively.

Physical Review AApr 1, 199895 citations

Measurements of Lowest-S-State Lifetimes of Gallium, Indium, and Thalium

Michael Norton, Alan C. Gallagher

The lifetimes of the gallium $5^{2}S_{\frac{1}{2}}$ state, the indium $6^{2}S_{\frac{1}{2}}$ state, and the thallium $7^{2}S_{\frac{1}{2}}$ state were measured using the zero-field level-crossing (Hanle-effect) technique. The life-times obtained were (6.8\ifmmode\pm\else\textpm\fi{}0.3) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}9}$, (7.0\ifmmode\pm\else\textpm\fi{}0.3) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}9}$, and (7.45\ifmmode\pm\else\textpm\fi{}0.2) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}9}$ sec, respectively. Anomalous contributions to the level-crossing signals, from the wavelength dependence of the exciting light intensity and self-absorption by the fluorescing atomic beam, were investigated in detail.The lifetimes of the gallium $5^{2}S_{\frac{1}{2}}$ state, the indium $6^{2}S_{\frac{1}{2}}$ state, and the thallium $7^{2}S_{\frac{1}{2}}$ state were measured using the zero-field level-crossing (Hanle-effect) technique. The life-times obtained were (6.8\ifmmode\pm\else\textpm\fi{}0.3) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}9}$, (7.0\ifmmode\pm\else\textpm\fi{}0.3) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}9}$, and (7.45\ifmmode\pm\else\textpm\fi{}0.2) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}9}$ sec, respectively. Anomalous contributions to the level-crossing signals, from the wavelength dependence of the exciting light intensity and self-absorption by the fluorescing atomic beam, were investigated in detail.

Physical Review AMar 1, 197134 citations

Lifetime of the 2P11 and 3P11 States of Atomic Helium

James M. Burger, Allen Lurio

The radiative lifetime of the $2^{1}P_{1}$ and $3^{1}P_{1}$ state of atomic helium has been measured by the level-crossing technique. In the experiment, a beam of $2^{1}S_{0}$ metastable atoms was first produced and then excited to the $2^{1}P_{1}$ or $3^{1}P_{1}$ state with resonance radiation. The lifetimes were measured by observing the zero-field level-crossing signals in the detected 584- or 537-\AA{} fluorescent radiation when these $^{1}P_{1}$ states decayed to the $1^{1}S_{0}$ ground state. The results are $\ensuremath{\tau} (2^{1}P_{1})=(5.57\ifmmode\pm\else\textpm\fi{}0.15)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$ sec and $\ensuremath{\tau} (3^{1}P_{1})=(1.73\ifmmode\pm\else\textpm\fi{}0.11)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}$ sec. These values are in excellent agreement with theory.The radiative lifetime of the $2^{1}P_{1}$ and $3^{1}P_{1}$ state of atomic helium has been measured by the level-crossing technique. In the experiment, a beam of $2^{1}S_{0}$ metastable atoms was first produced and then excited to the $2^{1}P_{1}$ or $3^{1}P_{1}$ state with resonance radiation. The lifetimes were measured by observing the zero-field level-crossing signals in the detected 584- or 537-\AA{} fluorescent radiation when these $^{1}P_{1}$ states decayed to the $1^{1}S_{0}$ ground state. The results are $\ensuremath{\tau} (2^{1}P_{1})=(5.57\ifmmode\pm\else\textpm\fi{}0.15)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$ sec and $\ensuremath{\tau} (3^{1}P_{1})=(1.73\ifmmode\pm\else\textpm\fi{}0.11)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}$ sec. These values are in excellent agreement with theory.

Physical Review AJan 1, 197121 citations

The lifetimes of the n

{\mathrm{}}^{2}$${P}_{1/2}

and n

{\mathrm{}}^{2}$${P}_{3/2}

^{2}\mathrm{P}

states are compared with other known experimental data and with the results of previous semiempirical calculations.

The lifetimes of the 7

{\mathrm{}}^{2}

{P}_{1/2}^{o}

and 7

{\mathrm{}}^{2}

{P}_{3/2}^{o}

states of thallium have been measured for the first time by observing the fluorescence decay following two-photon resonant excitation in an atomic beam. The values obtained for these states are 61.9 and 48.4 ns, respectively, with an uncertainty of 2%. These results are in good quantitative agreement with the calculations of Bardsley and Norcross, which include the effect of core polarizability.

We provide a detailed description of our fast-beam laser lifetime measurements in atomic cesium. Selective excitation of the neutral

{}^{133}\mathrm{Cs}

6p{}^{2}{P}_{1/2}

and

6p{}^{2}{P}_{3/2}

states is accomplished with resonant diode laser light directed transversely to the atomic velocity. The in-flight decay of the excited-state fluorescence is observed with a position-correlated single photon-counting detector. The Doppler-shifted

6p{}^{2}{P}_{3/2}

resonance, when probed with longitudinally propagating laser radiation, provides a precise means for determination of the beam velocity, and converts the position scale to a time scale. Our lifetime results are $35.07\ifmmode\pm\else\textpm\fi{}0.10 \mathrm{ns}$ for the

6p{}^{2}{P}_{1/2}

state and $30.57\ifmmode\pm\else\textpm\fi{}0.07 \mathrm{ns}$ for the

6p{}^{2}{P}_{3/2}

state. These results represent a data set larger than in our previous work, and include beam divergence corrections which have been evaluated by two different methods. We present comparisons of our results with previous measurements and with relativistic many-body calculations of atomic transition matrix elements in this neutral alkali system.

We present lifetime measurements of the

{7p}^{2}{P}_{3/2}

and

{7p}^{2}{P}_{1/2}

levels of Fr. We use a time-correlated single-photon counting technique on a cold sample of

{}^{210}\mathrm{Fr}

atoms in a magneto-optic trap. We excite the atoms with the trapping and repumping beams of the magneto-optic trap and detect the decay of the atomic fluorescence. The results are a precision experimental test of the atomic many-body perturbation theory applied to the heaviest alkali metal. The lifetime results are 21.02(11) ns and 29.45(11) ns for the

{7p}^{2}{P}_{3/2}

and

{7p}^{2}{P}_{1/2}

levels, respectively. This gives a line strength ratio

{\mathcal{S}}_{1/2}

{\mathcal{S}}_{3/2}

of 0.526(3) for these levels in Fr. To study sources of systematic errors we measure the lifetimes of

{5p}^{2}{P}_{3/2}

and

{5p}^{2}{P}_{1/2}

in stable

{}^{87}\mathrm{Rb}

and obtain 26.20(9) ns and 27.64(4) ns, respectively.

The lifetimes of the gallium

5^{2}S_{\frac{1}{2}}

state, the indium

6^{2}S_{\frac{1}{2}}

state, and the thallium

7^{2}S_{\frac{1}{2}}

state were measured using the zero-field level-crossing (Hanle-effect) technique. The life-times obtained were (6.8\ifmmode\pm\else\textpm\fi{}0.3) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}9}$, (7.0\ifmmode\pm\else\textpm\fi{}0.3) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}9}$, and (7.45\ifmmode\pm\else\textpm\fi{}0.2) \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}9}$ sec, respectively. Anomalous contributions to the level-crossing signals, from the wavelength dependence of the exciting light intensity and self-absorption by the fluorescing atomic beam, were investigated in detail.

The radiative lifetime of the

2^{1}P_{1}

and

3^{1}P_{1}

state of atomic helium has been measured by the level-crossing technique. In the experiment, a beam of

2^{1}S_{0}

metastable atoms was first produced and then excited to the

2^{1}P_{1}

3^{1}P_{1}

state with resonance radiation. The lifetimes were measured by observing the zero-field level-crossing signals in the detected 584- or 537-\AA{} fluorescent radiation when these

^{1}P_{1}

states decayed to the

1^{1}S_{0}

ground state. The results are $\ensuremath{\tau} (2^{1}P_{1})=(5.57\ifmmode\pm\else\textpm\fi{}0.15)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}$ sec and $\ensuremath{\tau} (3^{1}P_{1})=(1.73\ifmmode\pm\else\textpm\fi{}0.11)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}$ sec. These values are in excellent agreement with theory.