Physical Review A

Absolute photoionization cross-section measurement of selectively excited magnesium

Daniel Joseph Bradley, C. H. Dugan, P. Ewart, A.F. Purdie

Published Apr 1, 1976• 58 citations

Abstract

We report the first absolute measurement of the cross section for photoionization from a selectively excited short-lived atomic singlet state. Employing two simultaneous tunable laser pulses, the $3s3p^{1}P_{1}^{o}\ensuremath{-}3{p}^{2}^{1}S_{0}$ autoionization resonance in MgI was found to have a peak cross section of (8\ifmmode\pm\else\textpm\fi{}4)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}16}$ ${\mathrm{cm}}^{2}$ at $\ensuremath{\lambda}300.9$ nm and a half-width of 2.5 nm. The measured ratio of the cross sections to the $3{p}^{2}^{1}S_{0}$ and $^{1}D_{2}$ states was 14:1. The effect of polarization of the lasers has been investigated and shown to provide a means of identifying the angular momentum states of autoionizing levels.

DOI: 10.1103/physreva.13.1416

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Physical Review A

Absolute photoionization cross-section measurement of selectively excited magnesium

Daniel Joseph Bradley, C. H. Dugan, P. Ewart, A.F. Purdie

Published Apr 1, 1976• 58 citations

Publisher

Abstract

We report the first absolute measurement of the cross section for photoionization from a selectively excited short-lived atomic singlet state. Employing two simultaneous tunable laser pulses, the

3s3p^{1}P_{1}^{o}\ensuremath{-}3{p}^{2}^{1}S_{0}

autoionization resonance in MgI was found to have a peak cross section of (8\ifmmode\pm\else\textpm\fi{}4)\ifmmode\times\else\texttimes\fi{}

{10}^{\ensuremath{-}16}

{\mathrm{cm}}^{2}

\ensuremath{\lambda}300.9

nm and a half-width of 2.5 nm. The measured ratio of the cross sections to the

3{p}^{2}^{1}S_{0}

and

^{1}D_{2}

states was 14:1. The effect of polarization of the lasers has been investigated and shown to provide a means of identifying the angular momentum states of autoionizing levels.

DOI: 10.1103/physreva.13.1416

Related papers

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Stéphane Aloïse, Patrick O’Keeffe, D. Cubaynes +2 more

Physical Review LettersJun 8, 200525 citations

Resonant photoionization of Ni I into autoionizing states

Peter Lievens, Erno Vandeweert, Peter Thoen +1 more

Two-step resonant photoionization of free Ni atoms is studied by one-color and two-color processes, using pulsed lasers with photon energies around half the ground-state ionization energy. Two-color two-step resonance ionization from the ground state a ${\mathrm{}}^{3}$ ${\mathit{F}}_{4}$ and the first metastable state a ${\mathrm{}}^{3}$ ${\mathit{D}}_{3}$ via the triplet states z ${\mathrm{}}^{3}$ ${\mathit{G}}_{3,4,5}^{0}$ was used to probe the autoionizing states just above the ionization limit. Several strong lines in the one-color ionization spectrum are explained as direct two-photon transitions to autoionizing states. Photoionization cross sections were deduced from saturation measurements. The large cross sections observed for specific one-color two-step transitions are due to the near double resonant excitation into autoionizing states. \textcopyright{} 1996 The American Physical Society.Two-step resonant photoionization of free Ni atoms is studied by one-color and two-color processes, using pulsed lasers with photon energies around half the ground-state ionization energy. Two-color two-step resonance ionization from the ground state a${\mathrm{}}^{3}$${\mathit{F}}_{4}$ and the first metastable state a${\mathrm{}}^{3}$${\mathit{D}}_{3}$ via the triplet states z${\mathrm{}}^{3}$${\mathit{G}}_{3,4,5}^{0}$ was used to probe the autoionizing states just above the ionization limit. Several strong lines in the one-color ionization spectrum are explained as direct two-photon transitions to autoionizing states. Photoionization cross sections were deduced from saturation measurements. The large cross sections observed for specific one-color two-step transitions are due to the near double resonant excitation into autoionizing states. \textcopyright{} 1996 The American Physical Society.

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Absolute measurement of the photoionization cross section of the excited 7S state of cesium

S. L. Gilbert, Martin Charles Noecker, Carl Wieman

We report the first measurement of the absolute cross section for photoionization of the $7S$ state of cesium. The measurement employed a new technique in which the density of the excited-state atoms was determined by the amount of fluorescence. The cross section for photoionization by 540-nm light is 1.14(10)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}19}$ ${\mathrm{cm}}^{2}$ . We also propose a second new technique for the absolute measurement of photoionization cross sections which is based on modulated fluorescence.We report the first measurement of the absolute cross section for photoionization of the $7S$ state of cesium. The measurement employed a new technique in which the density of the excited-state atoms was determined by the amount of fluorescence. The cross section for photoionization by 540-nm light is 1.14(10)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}19}$ ${\mathrm{cm}}^{2}$. We also propose a second new technique for the absolute measurement of photoionization cross sections which is based on modulated fluorescence.

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Short-pulse photoionization of perturbed Rydberg states: Laser-induced autoionization

Rutger B. Vrijen, J. H. Hoogenraad, Lambertus D. Noordam

Laser-induced autoionization, a form of forced autoionization, is discussed. Highly excited atomic Rydberg states generally have a small cross section for photoionization due to their small overlap with the nucleus. The cross section for photoionization can be strongly enhanced if the Rydberg series is perturbed by an atomic state with a relatively large cross section for photoionization. The photoionization dynamics of such a perturbed Rydberg system shows strong similarities to that of an autoionizing Rydberg series. For intense laser pulses, which strongly couple the perturber to the continuum, the photoionization rate is limited by the coupling between the Rydberg states and the perturber or, in other words, the autoionization rate. The model describing this ionization dynamics is applied to the barium 6snd ${(}^{1,3}$ ${\mathit{D}}_{2}$ ) state which is perturbed by the 5d7d ${(}^{1}$ ${\mathit{D}}_{2}$ ) state. The calculations show good agreement with experimental results of photoionization of barium Rydberg states with subpicosecond laser pulses of light of 620 nm in wavelength.Laser-induced autoionization, a form of forced autoionization, is discussed. Highly excited atomic Rydberg states generally have a small cross section for photoionization due to their small overlap with the nucleus. The cross section for photoionization can be strongly enhanced if the Rydberg series is perturbed by an atomic state with a relatively large cross section for photoionization. The photoionization dynamics of such a perturbed Rydberg system shows strong similarities to that of an autoionizing Rydberg series. For intense laser pulses, which strongly couple the perturber to the continuum, the photoionization rate is limited by the coupling between the Rydberg states and the perturber or, in other words, the autoionization rate. The model describing this ionization dynamics is applied to the barium 6snd${(}^{1,3}$${\mathit{D}}_{2}$) state which is perturbed by the 5d7d${(}^{1}$${\mathit{D}}_{2}$) state. The calculations show good agreement with experimental results of photoionization of barium Rydberg states with subpicosecond laser pulses of light of 620 nm in wavelength.

Physical Review ASep 1, 19957 citations

Measurement of photoionization cross section in atomic uranium using simultaneous observation of laser-induced photoionization and fluorescence signals

M.L. Shah, Gomati Prasad Gupta, Vas Dev +3 more

Laser-induced photoionization and fluorescence signals were simultaneously observed in atomic uranium using a single Nd:YAG-pumped dye laser. These signals were recorded in two specific cases. In the first case, the dye laser was resonant to the first-step transition (0–16900.38 cm−1). In the second case, the laser was near-resonant to the first-step transition with a slight detuning (0.15 cm−1) so that it became two-photon resonant at 33801.06 cm−1. The uranium atoms in the ground state were ionized by a single-color, three-photon photoionization technique resulting in the photoionization signal, and the fluorescence signal was simultaneously obtained from the first excited state involved in the photoionization process. The photoionization and the fluorescence signals in the above-mentioned cases were also estimated theoretically for several values of the photoionization cross section for the transition between the second excited state at 33801.06 cm−1 and the autoionization state at 50701.59 cm−1 using density matrix formalism. From the comparison of theoretically calculated ratios of fluorescence signals in the two specific cases with the experimentally obtained values, the photoionization cross section for the 33801.06–50701.59 cm−1 transition has been obtained, which is found to be (5±1)×10−16 cm2.Laser-induced photoionization and fluorescence signals were simultaneously observed in atomic uranium using a single Nd:YAG-pumped dye laser. These signals were recorded in two specific cases. In the first case, the dye laser was resonant to the first-step transition (0–16900.38 cm−1). In the second case, the laser was near-resonant to the first-step transition with a slight detuning (0.15 cm−1) so that it became two-photon resonant at 33801.06 cm−1. The uranium atoms in the ground state were ionized by a single-color, three-photon photoionization technique resulting in the photoionization signal, and the fluorescence signal was simultaneously obtained from the first excited state involved in the photoionization process. The photoionization and the fluorescence signals in the above-mentioned cases were also estimated theoretically for several values of the photoionization cross section for the transition between the second excited state at 33801.06 cm−1 and the autoionization state at 50701.59 cm−1 using density matrix formalism. From the comparison of theoretically calculated ratios of fluorescence signals in the two specific cases with the experimentally obtained values, the photoionization cross section for the 33801.06–50701.59 cm−1 transition has been obtained, which is found to be (5±1)×10−16 cm2.

Journal of the Optical Society of America BMar 16, 20124 citations

We report the first absolute measurement of the cross section for photoionization from a selectively excited short-lived atomic singlet state. Employing two simultaneous tunable laser pulses, the

3s3p^{1}P_{1}^{o}\ensuremath{-}3{p}^{2}^{1}S_{0}

autoionization resonance in MgI was found to have a peak cross section of (8\ifmmode\pm\else\textpm\fi{}4)\ifmmode\times\else\texttimes\fi{}

{10}^{\ensuremath{-}16}

{\mathrm{cm}}^{2}

\ensuremath{\lambda}300.9

nm and a half-width of 2.5 nm. The measured ratio of the cross sections to the

3{p}^{2}^{1}S_{0}

and

^{1}D_{2}

states was 14:1. The effect of polarization of the lasers has been investigated and shown to provide a means of identifying the angular momentum states of autoionizing levels.

{\mathrm{}}^{3}

{\mathit{F}}_{4}

and the first metastable state a

{\mathrm{}}^{3}

{\mathit{D}}_{3}

via the triplet states z

{\mathrm{}}^{3}

{\mathit{G}}_{3,4,5}^{0}

was used to probe the autoionizing states just above the ionization limit. Several strong lines in the one-color ionization spectrum are explained as direct two-photon transitions to autoionizing states. Photoionization cross sections were deduced from saturation measurements. The large cross sections observed for specific one-color two-step transitions are due to the near double resonant excitation into autoionizing states. \textcopyright{} 1996 The American Physical Society.

We report the first measurement of the absolute cross section for photoionization of the

7S

state of cesium. The measurement employed a new technique in which the density of the excited-state atoms was determined by the amount of fluorescence. The cross section for photoionization by 540-nm light is 1.14(10)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}19}$

{\mathrm{cm}}^{2}

. We also propose a second new technique for the absolute measurement of photoionization cross sections which is based on modulated fluorescence.

{(}^{1,3}

{\mathit{D}}_{2}

) state which is perturbed by the 5d7d

{(}^{1}

{\mathit{D}}_{2}

) state. The calculations show good agreement with experimental results of photoionization of barium Rydberg states with subpicosecond laser pulses of light of 620 nm in wavelength.