Physical Review Letters

Effects of Electric Fields upon Autoionizing States of Sr

Richard R. Freeman, Gary C. Bjorklund

Published Jan 9, 1978• 45 citations

Abstract

We report the first observation of significant perturbations by external fields of the autoionizing resonance structure of a two-electron atoms. The effects of electric fields up to 20 kV/cm on autoionizing resonances in Sri were observed by three-photon ionization spectroscopy in an atomic beam. In addition to effects analogous to those for bound Stark states of a one-electron Rydberg atom, we observed a new effect: The characteristic shapes and widths of autoionizing resonances (Fano-Beutler profiles) can be strongly influenced by electric fields.

DOI: 10.1103/physrevlett.40.118

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Physical Review Letters

Effects of Electric Fields upon Autoionizing States of Sr

Richard R. Freeman, Gary C. Bjorklund

Published Jan 9, 1978• 45 citations

Publisher

Abstract

DOI: 10.1103/physrevlett.40.118

Related papers

Investigation of the Stark effect in krypton autoionizing Rydberg series with the use of two-step laser excitation

Christian Delsart, Jean-Claude Keller

The first detailed observation of the perturbations by an electric field of the Rydberg autoionizing resonances of a rare-gas atom is reported. The Stark spectroscopy of autoionizing Rydberg states converging to the second ionization limit $4{p}^{5}^{2}P_{\frac{1}{2}}^{o}$ in Kr I is performed in an atomic beam with the use of a two-step laser excitation from the $4{p}^{5}5s{[\frac{3}{2}]}_{2}^{0}$ metastable state. In addition to the verification of the ${({n}^{*})}^{\ensuremath{-}3}$ dependence of the zero-field width of two autoionizing series and of the linear dependence of the Stark-manifold splittings with the electric field, we have observed an ${(n)}^{0.7}$ law for the dependence of the Stark-manifold splitting along the series, an important narrowing and dissymmetrization of the $n{d}^{\ensuremath{'}}$ resonances, and a nonlinear-field behavior of Stark-manifold components in the vicinity of the first anticrossing. Discussions are carried out with the use of the recent work on Rydberg-Stark spectroscopy and on autoionizing states in two-electron atoms.The first detailed observation of the perturbations by an electric field of the Rydberg autoionizing resonances of a rare-gas atom is reported. The Stark spectroscopy of autoionizing Rydberg states converging to the second ionization limit $4{p}^{5}^{2}P_{\frac{1}{2}}^{o}$ in Kr I is performed in an atomic beam with the use of a two-step laser excitation from the $4{p}^{5}5s{[\frac{3}{2}]}_{2}^{0}$ metastable state. In addition to the verification of the ${({n}^{*})}^{\ensuremath{-}3}$ dependence of the zero-field width of two autoionizing series and of the linear dependence of the Stark-manifold splittings with the electric field, we have observed an ${(n)}^{0.7}$ law for the dependence of the Stark-manifold splitting along the series, an important narrowing and dissymmetrization of the $n{d}^{\ensuremath{'}}$ resonances, and a nonlinear-field behavior of Stark-manifold components in the vicinity of the first anticrossing. Discussions are carried out with the use of the recent work on Rydberg-Stark spectroscopy and on autoionizing states in two-electron atoms.

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The Stark spectra of autoionizing Rydberg states of Xe converging to the second ionization limit 5 ${p}^{5}$ $^{2}P_{1/2}$ have been investigated as a function of applied electric field over the range 26--2362 V/cm. Single-photon excitation from the Xe ground state was achieved using coherent radiation near 92.5 nm, generated by frequency tripling the pulsed output of a frequency-doubled dye laser in a free jet of rare-gas atoms. For the lowest electric field only the ns' and nd' series were observed. As the electric field was increased the np' series appeared because of the mixing of wave functions with different l values. Further increase of the electric field caused the appearance of hydrogenlike Stark manifolds. The Stark spectrum was simulated in a two-step procedure with no adjustable parameters. Using a jl-coupling basis set the Hamiltonian matrix was diagonalized to determine the energy levels and corresponding eigenfunctions for a given electric field strength. The intensities and line shapes were then calculated using the formalism developed by Fano for a many-discrete-level--single-continuum configuration interaction. This treatment was sufficient to reproduce the positions, widths, and shapes of most observed features. At field strengths between 1000 and 2000 V/cm, however, an additional modulation structure with a spacing of about 2.7 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ appeared on top of the \ensuremath{\Vert}M\ensuremath{\Vert}=1 autoionizing resonances, which could not be explained by our simple theoretical model.The Stark spectra of autoionizing Rydberg states of Xe converging to the second ionization limit 5${p}^{5}$ $^{2}P_{1/2}$ have been investigated as a function of applied electric field over the range 26--2362 V/cm. Single-photon excitation from the Xe ground state was achieved using coherent radiation near 92.5 nm, generated by frequency tripling the pulsed output of a frequency-doubled dye laser in a free jet of rare-gas atoms. For the lowest electric field only the ns' and nd' series were observed. As the electric field was increased the np' series appeared because of the mixing of wave functions with different l values. Further increase of the electric field caused the appearance of hydrogenlike Stark manifolds. The Stark spectrum was simulated in a two-step procedure with no adjustable parameters. Using a jl-coupling basis set the Hamiltonian matrix was diagonalized to determine the energy levels and corresponding eigenfunctions for a given electric field strength. The intensities and line shapes were then calculated using the formalism developed by Fano for a many-discrete-level--single-continuum configuration interaction. This treatment was sufficient to reproduce the positions, widths, and shapes of most observed features. At field strengths between 1000 and 2000 V/cm, however, an additional modulation structure with a spacing of about 2.7 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ appeared on top of the \ensuremath{\Vert}M\ensuremath{\Vert}=1 autoionizing resonances, which could not be explained by our simple theoretical model.

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Photoionization spectroscopy of Yb I from the 6s7sS01 state in the presence of a static electric field

Christophe Blondel, René-Jean Champeau, Christian Delsart

Laser investigation of the photoionization spectra in the presence of an electric field has been performed in $\ensuremath{\pi}$ and $\ensuremath{\sigma}$ polarizations on an ytterbium atomic beam from the particular level $4{f}^{14}6s7s^{1}S_{0}$ which was populated by a two-step excitation. Broad modulations (in $\ensuremath{\pi}$ polarization) and Stark resonances in the vicinity of the zero-field ionization limit are interpreted satisfactorily as in the case of alkali atoms. However, the photoionization spectra are deeply affected by the presence of two perturbing levels belonging to the configuration $4{f}^{13}5{d}^{2}6s$ . This phenomenon is explained by strong interference effects between the structured Stark continuum and the field-induced autoionizing states corresponding to the doubly excited levels.Laser investigation of the photoionization spectra in the presence of an electric field has been performed in $\ensuremath{\pi}$ and $\ensuremath{\sigma}$ polarizations on an ytterbium atomic beam from the particular level $4{f}^{14}6s7s^{1}S_{0}$ which was populated by a two-step excitation. Broad modulations (in $\ensuremath{\pi}$ polarization) and Stark resonances in the vicinity of the zero-field ionization limit are interpreted satisfactorily as in the case of alkali atoms. However, the photoionization spectra are deeply affected by the presence of two perturbing levels belonging to the configuration $4{f}^{13}5{d}^{2}6s$. This phenomenon is explained by strong interference effects between the structured Stark continuum and the field-induced autoionizing states corresponding to the doubly excited levels.

Physical Review AJan 1, 198312 citations

4{p}^{5}5s{[\frac{3}{2}]}_{2}^{0}

metastable state. In addition to the verification of the ${({n}^{*})}^{\ensuremath{-}3}$ dependence of the zero-field width of two autoionizing series and of the linear dependence of the Stark-manifold splittings with the electric field, we have observed an

{(n)}^{0.7}

law for the dependence of the Stark-manifold splitting along the series, an important narrowing and dissymmetrization of the $n{d}^{\ensuremath{'}}$ resonances, and a nonlinear-field behavior of Stark-manifold components in the vicinity of the first anticrossing. Discussions are carried out with the use of the recent work on Rydberg-Stark spectroscopy and on autoionizing states in two-electron atoms.

We report the effects of static electric fields on the doubly excited

6{p}_{\frac{1}{2}}\mathrm{nl}

states of barium in the region

{n}^{*}=12

. Using a three-step laser excitation scheme we have measured the electric-field dependence of the positions and autoionization widths of the $6{p}_{\frac{1}{2}}\ensuremath{-}17s,16p,15d,12l (l=4\ensuremath{-}10),12f, \mathrm{and} 16s$ states at field values of up to 4.92 kV/cm. The photoexcitation spectra of the autoionizing states exhibit interference effects which are well understood and provide a better understanding of the character of these states in electric fields. The systematic study of the spectra and positions allows us to explain the field dependence of the autoionization widths in terms of electric-field mixing of the discrete portions of the auoionizing states. The relationship of these effects to dielectronic recombination rates of ions and electrons in plasma microfields is discussed.

The Stark spectra of autoionizing Rydberg states of Xe converging to the second ionization limit 5

{p}^{5}

^{2}P_{1/2}

have been investigated as a function of applied electric field over the range 26--2362 V/cm. Single-photon excitation from the Xe ground state was achieved using coherent radiation near 92.5 nm, generated by frequency tripling the pulsed output of a frequency-doubled dye laser in a free jet of rare-gas atoms. For the lowest electric field only the ns' and nd' series were observed. As the electric field was increased the np' series appeared because of the mixing of wave functions with different l values. Further increase of the electric field caused the appearance of hydrogenlike Stark manifolds. The Stark spectrum was simulated in a two-step procedure with no adjustable parameters. Using a jl-coupling basis set the Hamiltonian matrix was diagonalized to determine the energy levels and corresponding eigenfunctions for a given electric field strength. The intensities and line shapes were then calculated using the formalism developed by Fano for a many-discrete-level--single-continuum configuration interaction. This treatment was sufficient to reproduce the positions, widths, and shapes of most observed features. At field strengths between 1000 and 2000 V/cm, however, an additional modulation structure with a spacing of about 2.7 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ appeared on top of the \ensuremath{\Vert}M\ensuremath{\Vert}=1 autoionizing resonances, which could not be explained by our simple theoretical model.

4{f}^{14}6s7s^{1}S_{0}

which was populated by a two-step excitation. Broad modulations (in $\ensuremath{\pi}$ polarization) and Stark resonances in the vicinity of the zero-field ionization limit are interpreted satisfactorily as in the case of alkali atoms. However, the photoionization spectra are deeply affected by the presence of two perturbing levels belonging to the configuration

4{f}^{13}5{d}^{2}6s

. This phenomenon is explained by strong interference effects between the structured Stark continuum and the field-induced autoionizing states corresponding to the doubly excited levels.