Physical Review A

Resonant photoionization of Ni I into autoionizing states

Peter Lievens, Erno Vandeweert, Peter Thoen, Roger E. Silverans

Published Sep 1, 1996• 26 citations

Abstract

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.

DOI: 10.1103/physreva.54.2253

Related papers

Progress in zirconium resonance ionization spectroscopy

Ralph H. Page, S. C. Dropinski, Earl F. Worden +1 more

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIEMay 28, 19936 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

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

Laser probe of the atomic ionization continuum: Stimulated recombination into an excited state

Burke Ritchie

Physical Review AOct 1, 198415 citations

Autoionizing states of negative ions in strong resonant laser fields: The negative rubidium ion

Henrik Stapelfeldt, Philip Trøst Kristensen, Ulric B. Ljungblad +2 more

Physical Review AAug 1, 199417 citations

Photoionization of Synchrotron-Radiation-Excited Atoms: Separating Partial Cross Sections by Full Polarization Control

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

Resonant atomic excitation by synchrotron radiation and subsequent ionization by a tunable dye laser is used to study the photoionization of short-lived Rydberg states in Xe. By combining circular and linear polarization of the synchrotron as well as of the laser photons the partial photoionization cross sections were separated in the region of overlapping autoionizing resonances of different symmetry and the parameters of the resonances were extracted.

Physical Review LettersJun 8, 200525 citations

Multiphoton excitation of autoionizing states of Mg: Line-shape studies of the 3 p2 S1 state

R. E. Bonanno, Charles W. Clark, Thomas B. Lucatorto

Physical Review ASep 1, 198650 citations

Physical Review A

Resonant photoionization of Ni I into autoionizing states

Peter Lievens, Erno Vandeweert, Peter Thoen, Roger E. Silverans

Published Sep 1, 1996• 26 citations

Publisher

Abstract

{\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.

DOI: 10.1103/physreva.54.2253

Related papers

Progress in zirconium resonance ionization spectroscopy

Ralph H. Page, S. C. Dropinski, Earl F. Worden +1 more

We have examined the stepwise-resonant three-photon-ionization spectrum of neutral Zirconium atoms using three separately-tunable pulsed visible dye lasers. The ground-level (first-step) transitions were chosen on the basis of demonstrated 91Zr selectivity. Lifetimes of even-parity levels around 36000 cm-1, measured with the delayed- photoionization technique, range from 10 to 100 nsec. Direct ionization cross sections appear to be less than 10-17 cm2; newly-detected autoionizing levels give peak ionization cross sections (inferred from saturation fluences) up to 10-15 cm2. Portions of Rydberg series converging to the 315 and 763 cm-1 levels of Zr+ were identified. 'Clumps' of autoionizing levels are thought to be due to Rydberg-valence mixing.We have examined the stepwise-resonant three-photon-ionization spectrum of neutral Zirconium atoms using three separately-tunable pulsed visible dye lasers. The ground-level (first-step) transitions were chosen on the basis of demonstrated 91Zr selectivity. Lifetimes of even-parity levels around 36000 cm-1, measured with the delayed- photoionization technique, range from 10 to 100 nsec. Direct ionization cross sections appear to be less than 10-17 cm2; newly-detected autoionizing levels give peak ionization cross sections (inferred from saturation fluences) up to 10-15 cm2. Portions of Rydberg series converging to the 315 and 763 cm-1 levels of Zr+ were identified. 'Clumps' of autoionizing levels are thought to be due to Rydberg-valence mixing.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIEMay 28, 19936 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

Laser probe of the atomic ionization continuum: Stimulated recombination into an excited state

Burke Ritchie

A two-laser theory is formulated for the photoionization of Li atoms. The first laser is tuned above the ionization threshold of $\mathrm{Li}(2s)$ . The second laser probes the ionized target. Stimulated recombination into $\mathrm{Li}(\mathrm{ns})$ occurs near the Raman-type resonance point ${\ensuremath{\epsilon}}_{\mathrm{ns}}\ensuremath{-}{\ensuremath{\epsilon}}_{2s}\ensuremath{-}{\ensuremath{\epsilon}}_{1}+{\ensuremath{\epsilon}}_{2}=0$ (where $n>2$ and ${\ensuremath{\epsilon}}_{q}$ is a photon energy). Near the resonance point the ionization probability is characterized by a line profile which resembles that for an autoionizing resonance.A two-laser theory is formulated for the photoionization of Li atoms. The first laser is tuned above the ionization threshold of $\mathrm{Li}(2s)$. The second laser probes the ionized target. Stimulated recombination into $\mathrm{Li}(\mathrm{ns})$ occurs near the Raman-type resonance point ${\ensuremath{\epsilon}}_{\mathrm{ns}}\ensuremath{-}{\ensuremath{\epsilon}}_{2s}\ensuremath{-}{\ensuremath{\epsilon}}_{1}+{\ensuremath{\epsilon}}_{2}=0$ (where $n>2$ and ${\ensuremath{\epsilon}}_{q}$ is a photon energy). Near the resonance point the ionization probability is characterized by a line profile which resembles that for an autoionizing resonance.

Physical Review AOct 1, 198415 citations

Autoionizing states of negative ions in strong resonant laser fields: The negative rubidium ion

Henrik Stapelfeldt, Philip Trøst Kristensen, Ulric B. Ljungblad +2 more

We have performed an experimental study of the atomic system ${\mathrm{Rb}}^{\mathrm{\ensuremath{-}}}$, for which the ground state 5 ${\mathit{s}}^{2}$ is coupled to the autoionizing state 5${\mathit{p}}_{1/2}$6s by means of a strong resonant laser field. The investigations are based on irradiation of ${\mathrm{Rb}}^{\mathrm{\ensuremath{-}}}$ with intense (I\ensuremath{\le}1.5\ifmmode\times\else\texttimes\fi{} ${10}^{10}$ W/ ${\mathrm{cm}}^{2}$ ) laser pulses of duration \ensuremath{\sim}1 ns. Single-photon detachment of ${\mathrm{Rb}}^{\mathrm{\ensuremath{-}}}$ is suppressed due to the Fano interference between transitions directly to the continuum and transitions via the autoionizing state. In contrast, two-photon absorption is at the same time resonantly enhanced since no such destructive interference is present in this process. These observations constitute experimental evidence of general features predicted from theoretical considerations of autoionizing states in strong laser fields. Furthermore, we discuss the role of autoionizing states in multiphoton double-ionization processes. Electron spectroscopy has been used to show that double ionization of ${\mathrm{Rb}}^{\mathrm{\ensuremath{-}}}$ primarily is the result of a sequential removal of the two electrons via an excited Rb state. The perspectives for direct two-electron ionization in negative ions are briefly discussed.We have performed an experimental study of the atomic system ${\mathrm{Rb}}^{\mathrm{\ensuremath{-}}}$, for which the ground state 5${\mathit{s}}^{2}$ is coupled to the autoionizing state 5${\mathit{p}}_{1/2}$6s by means of a strong resonant laser field. The investigations are based on irradiation of ${\mathrm{Rb}}^{\mathrm{\ensuremath{-}}}$ with intense (I\ensuremath{\le}1.5\ifmmode\times\else\texttimes\fi{}${10}^{10}$ W/${\mathrm{cm}}^{2}$) laser pulses of duration \ensuremath{\sim}1 ns. Single-photon detachment of ${\mathrm{Rb}}^{\mathrm{\ensuremath{-}}}$ is suppressed due to the Fano interference between transitions directly to the continuum and transitions via the autoionizing state. In contrast, two-photon absorption is at the same time resonantly enhanced since no such destructive interference is present in this process. These observations constitute experimental evidence of general features predicted from theoretical considerations of autoionizing states in strong laser fields. Furthermore, we discuss the role of autoionizing states in multiphoton double-ionization processes. Electron spectroscopy has been used to show that double ionization of ${\mathrm{Rb}}^{\mathrm{\ensuremath{-}}}$ primarily is the result of a sequential removal of the two electrons via an excited Rb state. The perspectives for direct two-electron ionization in negative ions are briefly discussed.

Physical Review AAug 1, 199417 citations

Photoionization of Synchrotron-Radiation-Excited Atoms: Separating Partial Cross Sections by Full Polarization Control

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

Physical Review LettersJun 8, 200525 citations

Multiphoton excitation of autoionizing states of Mg: Line-shape studies of the 3 p2 S1 state

R. E. Bonanno, Charles W. Clark, Thomas B. Lucatorto

We have observed ionization of Mg by both direct and stepwise two-photon excitation of the 3 ${p}^{2}$ ${\mathrm{}}^{1}$ S state. The line shape of the single-color direct process is strongly modified by the resonance denominator associated with the intermediate virtual state. The measured energy and width of this resonance as determined by the stepwise two-color technique agree well with previous determinations.We have observed ionization of Mg by both direct and stepwise two-photon excitation of the 3${p}^{2}$ ${\mathrm{}}^{1}$S state. The line shape of the single-color direct process is strongly modified by the resonance denominator associated with the intermediate virtual state. The measured energy and width of this resonance as determined by the stepwise two-color technique agree well with previous determinations.

Physical Review ASep 1, 198650 citations

A two-laser theory is formulated for the photoionization of Li atoms. The first laser is tuned above the ionization threshold of

\mathrm{Li}(2s)

. The second laser probes the ionized target. Stimulated recombination into

\mathrm{Li}(\mathrm{ns})

occurs near the Raman-type resonance point ${\ensuremath{\epsilon}}_{\mathrm{ns}}\ensuremath{-}{\ensuremath{\epsilon}}_{2s}\ensuremath{-}{\ensuremath{\epsilon}}_{1}+{\ensuremath{\epsilon}}_{2}=0$ (where

n>2

and ${\ensuremath{\epsilon}}_{q}$ is a photon energy). Near the resonance point the ionization probability is characterized by a line profile which resembles that for an autoionizing resonance.

We have performed an experimental study of the atomic system ${\mathrm{Rb}}^{\mathrm{\ensuremath{-}}}$, for which the ground state 5

{\mathit{s}}^{2}

is coupled to the autoionizing state 5${\mathit{p}}_{1/2}$6s by means of a strong resonant laser field. The investigations are based on irradiation of ${\mathrm{Rb}}^{\mathrm{\ensuremath{-}}}$ with intense (I\ensuremath{\le}1.5\ifmmode\times\else\texttimes\fi{}

{10}^{10}

{\mathrm{cm}}^{2}

) laser pulses of duration \ensuremath{\sim}1 ns. Single-photon detachment of ${\mathrm{Rb}}^{\mathrm{\ensuremath{-}}}$ is suppressed due to the Fano interference between transitions directly to the continuum and transitions via the autoionizing state. In contrast, two-photon absorption is at the same time resonantly enhanced since no such destructive interference is present in this process. These observations constitute experimental evidence of general features predicted from theoretical considerations of autoionizing states in strong laser fields. Furthermore, we discuss the role of autoionizing states in multiphoton double-ionization processes. Electron spectroscopy has been used to show that double ionization of ${\mathrm{Rb}}^{\mathrm{\ensuremath{-}}}$ primarily is the result of a sequential removal of the two electrons via an excited Rb state. The perspectives for direct two-electron ionization in negative ions are briefly discussed.

We have observed ionization of Mg by both direct and stepwise two-photon excitation of the 3

{p}^{2}

{\mathrm{}}^{1}

S state. The line shape of the single-color direct process is strongly modified by the resonance denominator associated with the intermediate virtual state. The measured energy and width of this resonance as determined by the stepwise two-color technique agree well with previous determinations.