Physical Review A

Lifetime measurements using the cascade-photon-coincidence technique with a sputtered-atom source

S. David Rosner, R. A. Holt, Timothy J. Scholl

Published May 1, 1997• 8 citations

Abstract

We have developed an interesting and widely applicable technique for measuring lifetimes of low-lying levels of neutral atoms and their first few ionization states. The cascade-photon-coincidence method has been extended by using a light source consisting of excited atoms sputtered from a solid by 10-keV argon ions. We have measured the lifetimes of the ${4\mathrm{p}}^{2}$${\mathrm{P}}_{3\mathrm{/}2}^{\mathrm{o}}$ state of Ca II, the ${6\mathrm{p}}^{2}$${\mathrm{P}}_{3\mathrm{/}2}^{\mathrm{o}}$ state of Ba II, and the ${4\mathrm{p}}^{2}$${\mathrm{P}}_{3\mathrm{/}2}^{\mathrm{o}}$ state of Al III. These measurements are in good agreement with earlier work.

DOI: 10.1103/physreva.55.3469

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Physical Review A

Lifetime measurements using the cascade-photon-coincidence technique with a sputtered-atom source

S. David Rosner, R. A. Holt, Timothy J. Scholl

Published May 1, 1997• 8 citations

Publisher

Abstract

{4\mathrm{p}}^{2}$${\mathrm{P}}_{3\mathrm{/}2}^{\mathrm{o}}

state of Ca II, the

{6\mathrm{p}}^{2}$${\mathrm{P}}_{3\mathrm{/}2}^{\mathrm{o}}

state of Ba II, and the

{4\mathrm{p}}^{2}$${\mathrm{P}}_{3\mathrm{/}2}^{\mathrm{o}}

state of Al III. These measurements are in good agreement with earlier work.

DOI: 10.1103/physreva.55.3469

Related papers

Measured Lifetime of the ( 3p54s ) P13 State of Argon

John L. Morack, Clifford E. Fairchild

A direct measurement of the natural lifetime for the ( $3{p}^{5}4s$ ) $^{3}P_{1}$ state of argon has been made using a modified delayed-coincidence method. Argon atoms are repetitively excited by pulses of electrons. For each pulse, the decaying light signal is sampled for a time $\ensuremath{\Delta}t$ at some delay time ${t}_{1}$ after the excitation is terminated. The exponential decay is then reconstructed as the delay time is changed. Collision effects are not important in the pressure region (5.0\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}6}$-2.0\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}4}$ Torr) of the experiment and the effects due to cascading are eliminated by keeping the energy of the bombarding electrons low enough so that excitation of the $3{p}^{5}4p$ levels is negligible. The measured lifetime is dependent upon the argon pressure, and this effect is attributed to resonance trapping; a value of 21\ifmmode\pm\else\textpm\fi{}2 nsec is obtained for the natural lifetime by using the existing theories of resonance trapping to extrapolate the data to zero pressure.A direct measurement of the natural lifetime for the ($3{p}^{5}4s$) $^{3}P_{1}$ state of argon has been made using a modified delayed-coincidence method. Argon atoms are repetitively excited by pulses of electrons. For each pulse, the decaying light signal is sampled for a time $\ensuremath{\Delta}t$ at some delay time ${t}_{1}$ after the excitation is terminated. The exponential decay is then reconstructed as the delay time is changed. Collision effects are not important in the pressure region (5.0\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}6}$-2.0\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}4}$ Torr) of the experiment and the effects due to cascading are eliminated by keeping the energy of the bombarding electrons low enough so that excitation of the $3{p}^{5}4p$ levels is negligible. The measured lifetime is dependent upon the argon pressure, and this effect is attributed to resonance trapping; a value of 21\ifmmode\pm\else\textpm\fi{}2 nsec is obtained for the natural lifetime by using the existing theories of resonance trapping to extrapolate the data to zero pressure.

Physical ReviewNov 5, 196718 citations

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David A. Shaw, GEORGE C. KING, A Adams

Journal of Physics B Atomic and Molecular PhysicsJan 28, 197812 citations

Oscillator Strengths of Ca II, Sr II, and Ba II

Alan C. Gallagher

The lifetimes of the $5p^{2}P_{\frac{3}{2}}$ and $5p^{2}P_{\frac{1}{2}}$ states of ${\mathrm{Sr}}^{+}$ and the $6p^{2}P_{\frac{3}{2}}$ and $6p^{2}P_{\frac{1}{2}}$ states of ${\mathrm{Ba}}^{+}$ have been measured by the Hanle-effect technique with optical excitation from the ion ground state. (The lifetimes of the ${\mathrm{Mg}}^{+}$ $3p^{2}P_{\frac{3}{2}}$ and ${\mathrm{Ca}}^{+}$ $4p^{2}P_{\frac{3}{2}}$ states were obtained by the same technique and reported previously.) These ${\mathrm{Ca}}^{+}$ , ${\mathrm{Sr}}^{+}$ , and ${\mathrm{Ba}}^{+}$ states each decay to a $^{2}D_{\frac{3}{2},\frac{5}{2}}$ doublet as well as to the ground $^{2}S_{\frac{1}{2}}$ state, and the branching ratios for these transitions have been measured. The ions were produced by introducing traces of the atomic vapor into an argon discharge. Consequently, the cross sections for collisional depolarization of these $^{2}P_{J}$ states due to collisions with argon were also obtained from the measurements. The experimental results are given in Tables I and II. A discussion of the ion-atom collisional depolarization cross sections is included.The lifetimes of the $5p^{2}P_{\frac{3}{2}}$ and $5p^{2}P_{\frac{1}{2}}$ states of ${\mathrm{Sr}}^{+}$ and the $6p^{2}P_{\frac{3}{2}}$ and $6p^{2}P_{\frac{1}{2}}$ states of ${\mathrm{Ba}}^{+}$ have been measured by the Hanle-effect technique with optical excitation from the ion ground state. (The lifetimes of the ${\mathrm{Mg}}^{+}$ $3p^{2}P_{\frac{3}{2}}$ and ${\mathrm{Ca}}^{+}$ $4p^{2}P_{\frac{3}{2}}$ states were obtained by the same technique and reported previously.) These ${\mathrm{Ca}}^{+}$, ${\mathrm{Sr}}^{+}$, and ${\mathrm{Ba}}^{+}$ states each decay to a $^{2}D_{\frac{3}{2},\frac{5}{2}}$ doublet as well as to the ground $^{2}S_{\frac{1}{2}}$ state, and the branching ratios for these transitions have been measured. The ions were produced by introducing traces of the atomic vapor into an argon discharge. Consequently, the cross sections for collisional depolarization of these $^{2}P_{J}$ states due to collisions with argon were also obtained from the measurements. The experimental results are given in Tables I and II. A discussion of the ion-atom collisional depolarization cross sections is included.

Physical ReviewMay 5, 1967217 citations

Lifetime measurement of the 6s level of rubidium

E. Gómez, F. Baumer, A. D. Lange +2 more

We present a lifetime measurement of the $6s$ level of rubidium. We use a time-correlated single-photon counting technique on two different samples of rubidium atoms, a vapor cell with variable rubidium density, and a sample of atoms confined and cooled in a magneto-optical trap. The $5{P}_{1∕2}$ level serves as the resonant intermediate step for the two-step excitation to the $6s$ level. We detect the decay of the $6s$ level through the cascade fluorescence of the $5{P}_{3∕2}$ level at 780 nm. The two samples have different systematic effects, but we obtain consistent results that averaged give a lifetime of $45.57\ifmmode\pm\else\textpm\fi{}0.17\phantom{\rule{0.3em}{0ex}}\mathrm{ns}$.We present a lifetime measurement of the $6s$ level of rubidium. We use a time-correlated single-photon counting technique on two different samples of rubidium atoms, a vapor cell with variable rubidium density, and a sample of atoms confined and cooled in a magneto-optical trap. The $5{P}_{1∕2}$ level serves as the resonant intermediate step for the two-step excitation to the $6s$ level. We detect the decay of the $6s$ level through the cascade fluorescence of the $5{P}_{3∕2}$ level at 780 nm. The two samples have different systematic effects, but we obtain consistent results that averaged give a lifetime of $45.57\ifmmode\pm\else\textpm\fi{}0.17\phantom{\rule{0.3em}{0ex}}\mathrm{ns}$.

arXiv:physics/0502090Physical Review AJul 1, 200531 citations

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

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

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.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.

Physical Review AAug 1, 198614 citations

A direct measurement of the natural lifetime for the (

3{p}^{5}4s

)

^{3}P_{1}

state of argon has been made using a modified delayed-coincidence method. Argon atoms are repetitively excited by pulses of electrons. For each pulse, the decaying light signal is sampled for a time $\ensuremath{\Delta}t$ at some delay time

{t}_{1}

after the excitation is terminated. The exponential decay is then reconstructed as the delay time is changed. Collision effects are not important in the pressure region (5.0\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}6}$-2.0\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}4}$ Torr) of the experiment and the effects due to cascading are eliminated by keeping the energy of the bombarding electrons low enough so that excitation of the

3{p}^{5}4p

levels is negligible. The measured lifetime is dependent upon the argon pressure, and this effect is attributed to resonance trapping; a value of 21\ifmmode\pm\else\textpm\fi{}2 nsec is obtained for the natural lifetime by using the existing theories of resonance trapping to extrapolate the data to zero pressure.

The lifetimes of the

5p^{2}P_{\frac{3}{2}}

and

5p^{2}P_{\frac{1}{2}}

states of

{\mathrm{Sr}}^{+}

and the

6p^{2}P_{\frac{3}{2}}

and

6p^{2}P_{\frac{1}{2}}

states of

{\mathrm{Ba}}^{+}

have been measured by the Hanle-effect technique with optical excitation from the ion ground state. (The lifetimes of the

{\mathrm{Mg}}^{+}

3p^{2}P_{\frac{3}{2}}

and

{\mathrm{Ca}}^{+}

4p^{2}P_{\frac{3}{2}}

states were obtained by the same technique and reported previously.) These

{\mathrm{Ca}}^{+}

{\mathrm{Sr}}^{+}

, and

{\mathrm{Ba}}^{+}

states each decay to a

^{2}D_{\frac{3}{2},\frac{5}{2}}

doublet as well as to the ground

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

state, and the branching ratios for these transitions have been measured. The ions were produced by introducing traces of the atomic vapor into an argon discharge. Consequently, the cross sections for collisional depolarization of these

^{2}P_{J}

states due to collisions with argon were also obtained from the measurements. The experimental results are given in Tables I and II. A discussion of the ion-atom collisional depolarization cross sections is included.

We present a lifetime measurement of the

6s

level of rubidium. We use a time-correlated single-photon counting technique on two different samples of rubidium atoms, a vapor cell with variable rubidium density, and a sample of atoms confined and cooled in a magneto-optical trap. The

5{P}_{1∕2}

level serves as the resonant intermediate step for the two-step excitation to the

6s

level. We detect the decay of the

6s

level through the cascade fluorescence of the

5{P}_{3∕2}

level at 780 nm. The two samples have different systematic effects, but we obtain consistent results that averaged give a lifetime of $45.57\ifmmode\pm\else\textpm\fi{}0.17\phantom{\rule{0.3em}{0ex}}\mathrm{ns}$.

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.