Physical Review A

Field ionization and forced autoionization of Li2

G. R. Janik, Oliver C. Mullins, Christopher R. Mahon, Thomas F. Gallagher

Published Mar 1, 1987• 36 citations

Abstract

Bound ${\mathrm{Li}}_{2}$ states of principal quantum number n=12--14 converging to v=2 and 3 levels of the ground state of ${\mathrm{Li}}_{2}$${\mathrm{}}^{+}$ can be ionized by fields of \ensuremath{\sim}200 V/cm, 2 orders of magnitude less than expected for direct field ionization of these levels. The result is shown to be due to forced autoionization. The field depresses the ionization limit of the series converging to the lowest rotational-vibrational ${\mathrm{Li}}_{2}$${\mathrm{}}^{+}$ levels, and the n=12--14 levels in question autoionize to the Stark-induced continuum.

DOI: 10.1103/physreva.35.2345

Related papers

Microwave forced autoionization of Na2 Rydberg states

Christopher R. Mahon, Chung Yi Lee, Thomas F. Gallagher

Physical Review ASep 1, 19931 citation

Stark-effect studies in xenon autoionizing Rydberg states using a tunable extreme-ultraviolet laser source

Wolfgang Ernst, T. P. Softley, Richard N. Zare

Physical Review AJun 1, 198878 citations

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

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

Physical Review ASep 1, 19957 citations

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

Christian Delsart, Jean-Claude Keller

Physical Review AAug 1, 198326 citations

Microwave Ionization of Na Rydberg Levels

P. Pillet, W. W. Smith, Ravinder Kachru +2 more

Physical Review LettersApr 4, 198346 citations

Autoionization Inhibited by Internal Interferences

Jörg Neukammer, Herbert H. Rinneberg, G. Jönsson +5 more

Physical Review LettersNov 4, 198553 citations

Physical Review A

Field ionization and forced autoionization of Li2

G. R. Janik, Oliver C. Mullins, Christopher R. Mahon, Thomas F. Gallagher

Published Mar 1, 1987• 36 citations

Publisher

Abstract

Bound

{\mathrm{Li}}_{2}

states of principal quantum number n=12--14 converging to v=2 and 3 levels of the ground state of

{\mathrm{Li}}_{2}$${\mathrm{}}^{+}

can be ionized by fields of \ensuremath{\sim}200 V/cm, 2 orders of magnitude less than expected for direct field ionization of these levels. The result is shown to be due to forced autoionization. The field depresses the ionization limit of the series converging to the lowest rotational-vibrational

{\mathrm{Li}}_{2}$${\mathrm{}}^{+}

levels, and the n=12--14 levels in question autoionize to the Stark-induced continuum.

DOI: 10.1103/physreva.35.2345

Related papers

Microwave forced autoionization of Na2 Rydberg states

Christopher R. Mahon, Chung Yi Lee, Thomas F. Gallagher

We have examined the ionization of ${\mathrm{Na}}_{2}$ Rydberg states of principal quantum number n=11--16 converging to rotational-vibrational, v=3--6 and R10, states of ${\mathrm{Na}}_{2}^{+}$ by 8-GHz microwave fields. Rydberg states lying below the lowest, v=0, R=0 (v and R are the vibrational and rotational quantum numbers of the molecular ion), ion limit of ${\mathrm{Na}}_{2}^{+}$ are observed to ionize at approximately E=1/3 ${\mathit{n}}_{0}^{5}$ , where ${\mathit{n}}_{0}$ is the effective quantum number relative to the v=R=0 limit. The agreement with this dependence is not nearly as good as in an atom, and the possible reasons for the deviations are discussed.We have examined the ionization of ${\mathrm{Na}}_{2}$ Rydberg states of principal quantum number n=11--16 converging to rotational-vibrational, v=3--6 and R10, states of ${\mathrm{Na}}_{2}^{+}$ by 8-GHz microwave fields. Rydberg states lying below the lowest, v=0, R=0 (v and R are the vibrational and rotational quantum numbers of the molecular ion), ion limit of ${\mathrm{Na}}_{2}^{+}$ are observed to ionize at approximately E=1/3${\mathit{n}}_{0}^{5}$, where ${\mathit{n}}_{0}$ is the effective quantum number relative to the v=R=0 limit. The agreement with this dependence is not nearly as good as in an atom, and the possible reasons for the deviations are discussed.

Physical Review ASep 1, 19931 citation

Stark-effect studies in xenon autoionizing Rydberg states using a tunable extreme-ultraviolet laser source

Wolfgang Ernst, T. P. Softley, Richard N. Zare

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.

Physical Review AJun 1, 198878 citations

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

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.

Physical Review AAug 1, 198326 citations

Microwave Ionization of Na Rydberg Levels

P. Pillet, W. W. Smith, Ravinder Kachru +2 more

The authors have observed the ionization of Na Rydberg states by strong microwave fields and have found that the field required for ionization is $\frac{1}{(3.7{n}^{5})}$ (in atomic units) for $n=20\ensuremath{-}37$. This field is close to the field $\frac{1}{(3{n}^{5})}$ at which the Stark manifolds of principal quantum numbers $n$ and $n+1$ intersect. The ionization can be shown to arise from transitions occurring near these intersections.The authors have observed the ionization of Na Rydberg states by strong microwave fields and have found that the field required for ionization is $\frac{1}{(3.7{n}^{5})}$ (in atomic units) for $n=20\ensuremath{-}37$. This field is close to the field $\frac{1}{(3{n}^{5})}$ at which the Stark manifolds of principal quantum numbers $n$ and $n+1$ intersect. The ionization can be shown to arise from transitions occurring near these intersections.

Physical Review LettersApr 4, 198346 citations

Autoionization Inhibited by Internal Interferences

Jörg Neukammer, Herbert H. Rinneberg, G. Jönsson +5 more

We have measured the linewidths of ${[5{d}_{\frac{3}{2}}{n}_{2}{d}_{\frac{3}{2}}]}_{J=0}$ autoionizing Rydberg states of barium with principal quantum numbers ranging between ${n}_{2}=14$ and ${n}_{2}=100$ . Dramatic deviations of the autoionization rates from the normal ${n}_{2}^{*\ensuremath{-}3}$ scaling law have been observed. Whereas the ${[5{d}_{\frac{3}{2}}60{d}_{\frac{3}{2}}]}_{J=0}$ level exhibits a linewidth $\ensuremath{\Gamma}$ (FWMH) as low as 6 MHz, higher (${n}_{2}\ensuremath{\approx}80$) members of this series are broadened up to 5 GHz. Autoionization is inhibited for principal quantum numbers ${n}_{2}\ensuremath{\approx}60$ because of configuration interaction between the ${[5{d}_{\frac{3}{2}}{n}_{2}{d}_{\frac{3}{2}}]}_{J=0}$ and ${[5{d}_{\frac{5}{2}}{n}_{3}{d}_{\frac{5}{2}}]}_{J=0}$ Rydberg series. This causes the state at ${n}_{2}=60$ to be metastable.We have measured the linewidths of ${[5{d}_{\frac{3}{2}}{n}_{2}{d}_{\frac{3}{2}}]}_{J=0}$ autoionizing Rydberg states of barium with principal quantum numbers ranging between ${n}_{2}=14$ and ${n}_{2}=100$. Dramatic deviations of the autoionization rates from the normal ${n}_{2}^{*\ensuremath{-}3}$ scaling law have been observed. Whereas the ${[5{d}_{\frac{3}{2}}60{d}_{\frac{3}{2}}]}_{J=0}$ level exhibits a linewidth $\ensuremath{\Gamma}$ (FWMH) as low as 6 MHz, higher (${n}_{2}\ensuremath{\approx}80$) members of this series are broadened up to 5 GHz. Autoionization is inhibited for principal quantum numbers ${n}_{2}\ensuremath{\approx}60$ because of configuration interaction between the ${[5{d}_{\frac{3}{2}}{n}_{2}{d}_{\frac{3}{2}}]}_{J=0}$ and ${[5{d}_{\frac{5}{2}}{n}_{3}{d}_{\frac{5}{2}}]}_{J=0}$ Rydberg series. This causes the state at ${n}_{2}=60$ to be metastable.

Physical Review LettersNov 4, 198553 citations

Bound

{\mathrm{Li}}_{2}

states of principal quantum number n=12--14 converging to v=2 and 3 levels of the ground state of

{\mathrm{Li}}_{2}$${\mathrm{}}^{+}

{\mathrm{Li}}_{2}$${\mathrm{}}^{+}

levels, and the n=12--14 levels in question autoionize to the Stark-induced continuum.

We have examined the ionization of

{\mathrm{Na}}_{2}

Rydberg states of principal quantum number n=11--16 converging to rotational-vibrational, v=3--6 and R10, states of

{\mathrm{Na}}_{2}^{+}

by 8-GHz microwave fields. Rydberg states lying below the lowest, v=0, R=0 (v and R are the vibrational and rotational quantum numbers of the molecular ion), ion limit of

{\mathrm{Na}}_{2}^{+}

are observed to ionize at approximately E=1/3

{\mathit{n}}_{0}^{5}

, where

{\mathit{n}}_{0}

is the effective quantum number relative to the v=R=0 limit. The agreement with this dependence is not nearly as good as in an atom, and the possible reasons for the deviations are 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.

{(}^{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.

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 authors have observed the ionization of Na Rydberg states by strong microwave fields and have found that the field required for ionization is

\frac{1}{(3.7{n}^{5})}

(in atomic units) for $n=20\ensuremath{-}37$. This field is close to the field

\frac{1}{(3{n}^{5})}

at which the Stark manifolds of principal quantum numbers

n

and

n+1

intersect. The ionization can be shown to arise from transitions occurring near these intersections.

We have measured the linewidths of

{[5{d}_{\frac{3}{2}}{n}_{2}{d}_{\frac{3}{2}}]}_{J=0}

autoionizing Rydberg states of barium with principal quantum numbers ranging between

{n}_{2}=14

and

{n}_{2}=100

. Dramatic deviations of the autoionization rates from the normal ${n}_{2}^{*\ensuremath{-}3}$ scaling law have been observed. Whereas the

{[5{d}_{\frac{3}{2}}60{d}_{\frac{3}{2}}]}_{J=0}

level exhibits a linewidth $\ensuremath{\Gamma}$ (FWMH) as low as 6 MHz, higher (${n}_{2}\ensuremath{\approx}80$) members of this series are broadened up to 5 GHz. Autoionization is inhibited for principal quantum numbers ${n}_{2}\ensuremath{\approx}60$ because of configuration interaction between the

{[5{d}_{\frac{3}{2}}{n}_{2}{d}_{\frac{3}{2}}]}_{J=0}

and

{[5{d}_{\frac{5}{2}}{n}_{3}{d}_{\frac{5}{2}}]}_{J=0}

Rydberg series. This causes the state at

{n}_{2}=60

to be metastable.