Physical Review Letters

Structural Properties of the Negative Calcium Ion:Binding Energies and Fine-Structure Splitting

V. V. Petrunin, H. H. Andersen, Péter Balling, T. Andersen

Published Jan 29, 1996• 91 citations

Abstract

The binding energies of the ${4s}^{2}4p^{2}P$ ground state in ${\mathrm{Ca}}^{\ensuremath{-}}$ have been determined by means of state-selective photoionization of Ca atoms produced in s-wave photodetachment to be $24.55\ifmmode\pm\else\textpm\fi{}0.10$ meV for the $J\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1/2$ and $19.73\ifmmode\pm\else\textpm\fi{}0.10$ meV for the $J\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}3/2$ component. The sensitivity of the detection technique applied has also made it possible to disprove previous claims for the observation of a metastable ${4s4p}^{2}^{4}P$ state in ${\mathrm{Ca}}^{\ensuremath{-}}$.

DOI: 10.1103/physrevlett.76.744

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Physical Review Letters

Structural Properties of the Negative Calcium Ion:Binding Energies and Fine-Structure Splitting

V. V. Petrunin, H. H. Andersen, Péter Balling, T. Andersen

Published Jan 29, 1996• 91 citations

Publisher

Abstract

The binding energies of the

{4s}^{2}4p^{2}P

ground state in

{\mathrm{Ca}}^{\ensuremath{-}}

have been determined by means of state-selective photoionization of Ca atoms produced in s-wave photodetachment to be

24.55\ifmmode\pm\else\textpm\fi{}0.10

meV for the

J\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1/2

and

19.73\ifmmode\pm\else\textpm\fi{}0.10

meV for the

J\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}3/2

component. The sensitivity of the detection technique applied has also made it possible to disprove previous claims for the observation of a metastable

{4s4p}^{2}^{4}P

state in

{\mathrm{Ca}}^{\ensuremath{-}}

DOI: 10.1103/physrevlett.76.744

Related papers

Structural properties of the negative strontium ion: Binding energy and fine-structure splitting

H. H. Andersen, V. V. Petrunin, P. Kristensen +1 more

The binding energy and fine-structure splitting of the ground state of the ${\mathrm{Sr}}^{\mathrm{\ensuremath{-}}}$n(${5\mathrm{s}}^{2} $5p$ {\mathrm{}}^{2}$P) ion have been measured by means of the laser photodetachment threshold technique combined with state-selective detection of neutral atoms using resonant ionization spectroscopy. We find binding energies of 32.17\ifmmode\pm\else\textpm\fi{}0.03 meV (J=3/2) and 52.06\ifmmode\pm\else\textpm\fi{}0.06 meV (J=1/2), yielding a fine-structure splitting of 19.89\ifmmode\pm\else\textpm\fi{}0.07 meV. This represents an improvement of two orders of magnitude compared to the recent data based on a combination of laser photodetachment and accelerator mass spectroscopy [D. Berkovits et al., Phys. Rev. Lett. 75, 414 (1995)].The binding energy and fine-structure splitting of the ground state of the ${\mathrm{Sr}}^{\mathrm{\ensuremath{-}}}$n(${5\mathrm{s}}^{2}$5p${\mathrm{}}^{2}$P) ion have been measured by means of the laser photodetachment threshold technique combined with state-selective detection of neutral atoms using resonant ionization spectroscopy. We find binding energies of 32.17\ifmmode\pm\else\textpm\fi{}0.03 meV (J=3/2) and 52.06\ifmmode\pm\else\textpm\fi{}0.06 meV (J=1/2), yielding a fine-structure splitting of 19.89\ifmmode\pm\else\textpm\fi{}0.07 meV. This represents an improvement of two orders of magnitude compared to the recent data based on a combination of laser photodetachment and accelerator mass spectroscopy [D. Berkovits et al., Phys. Rev. Lett. 75, 414 (1995)].

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Physical Review AOct 1, 198923 citations

Electron Affinity of Strontium

D. Berkovits, Elisabetta Boaretto, S. Ghelberg +2 more

We have observed a threshold in the electron photodetachment cross section of ${^{88}S\mathrm{r}}^{\ensuremath{-}}$ ions at a photon energy $h\ensuremath{\nu}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.820\mathrm{eV}$ and assign it to a $p$ -wave transition from the ${5s}^{2}5p^{2}P$ ground state in ${\mathrm{Sr}}^{\ensuremath{-}}$ to the $5s5p^{3}P$ state in neutral Sr. The measurement was made with a new technique combining the tunable laser photodetachment threshold method with accelerator mass spectrometry. We determine for the first time the electron affinity of Sr to be $48\ifmmode\pm\else\textpm\fi{}6\mathrm{meV}$, much smaller than predicted in recent calculations. The $^{2}P_{1/2}$ - $^{2}P_{3/2}$ fine splitting of the ${\mathrm{Sr}}^{\ensuremath{-}}$ ground state is estimated to be $26\ifmmode\pm\else\textpm\fi{}8\mathrm{meV}$.We have observed a threshold in the electron photodetachment cross section of ${^{88}S\mathrm{r}}^{\ensuremath{-}}$ ions at a photon energy $h\ensuremath{\nu}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.820\mathrm{eV}$ and assign it to a $p$-wave transition from the ${5s}^{2}5p^{2}P$ ground state in ${\mathrm{Sr}}^{\ensuremath{-}}$ to the $5s5p^{3}P$ state in neutral Sr. The measurement was made with a new technique combining the tunable laser photodetachment threshold method with accelerator mass spectrometry. We determine for the first time the electron affinity of Sr to be $48\ifmmode\pm\else\textpm\fi{}6\mathrm{meV}$, much smaller than predicted in recent calculations. The $^{2}P_{1/2}$- $^{2}P_{3/2}$ fine splitting of the ${\mathrm{Sr}}^{\ensuremath{-}}$ ground state is estimated to be $26\ifmmode\pm\else\textpm\fi{}8\mathrm{meV}$.

Physical Review LettersJul 17, 199525 citations

Evidence for resonant formation of Ca− in collisions of Rydberg and ground-state Ca atoms

K. W. McLaughlin, D. W. Duquette

Relative yields of ${\mathrm{Ca}}^{+}$ and ${\mathrm{Ca}}^{\mathrm{\ensuremath{-}}}$ ions from thermal-energy collisions between highly excited ${\mathrm{Ca}}^{\mathrm{*}}$ 4snd $^{1}$ D Rydberg atoms and Ca ground-state atoms are measured as a function of n. The collisions take place within an effusive Ca atomic beam. The cross section for a collision resulting in a bound ${\mathrm{Ca}}^{\mathrm{\ensuremath{-}}}$ and a ground-state ${\mathrm{Ca}}^{+}$ is expected to be large when the binding energy of the excited Rydberg state nearly matches the electron affinity of Ca. We observe a large increase in positive and negative ions for n=25 only. This result strongly suggests that the binding energy of ${\mathrm{Ca}}^{\mathrm{\ensuremath{-}}}$ is 24\ifmmode\pm\else\textpm\fi{}1.4 meV.Relative yields of ${\mathrm{Ca}}^{+}$ and ${\mathrm{Ca}}^{\mathrm{\ensuremath{-}}}$ ions from thermal-energy collisions between highly excited ${\mathrm{Ca}}^{\mathrm{*}}$ 4snd $^{1}$D Rydberg atoms and Ca ground-state atoms are measured as a function of n. The collisions take place within an effusive Ca atomic beam. The cross section for a collision resulting in a bound ${\mathrm{Ca}}^{\mathrm{\ensuremath{-}}}$ and a ground-state ${\mathrm{Ca}}^{+}$ is expected to be large when the binding energy of the excited Rydberg state nearly matches the electron affinity of Ca. We observe a large increase in positive and negative ions for n=25 only. This result strongly suggests that the binding energy of ${\mathrm{Ca}}^{\mathrm{\ensuremath{-}}}$ is 24\ifmmode\pm\else\textpm\fi{}1.4 meV.

Physical Review LettersFeb 21, 199435 citations

The binding energies of the

{4s}^{2}4p^{2}P

ground state in

{\mathrm{Ca}}^{\ensuremath{-}}

have been determined by means of state-selective photoionization of Ca atoms produced in s-wave photodetachment to be

24.55\ifmmode\pm\else\textpm\fi{}0.10

meV for the

J\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1/2

and

19.73\ifmmode\pm\else\textpm\fi{}0.10

meV for the

J\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}3/2

component. The sensitivity of the detection technique applied has also made it possible to disprove previous claims for the observation of a metastable

{4s4p}^{2}^{4}P

state in

{\mathrm{Ca}}^{\ensuremath{-}}

The binding energy and fine-structure splitting of the ground state of the ${\mathrm{Sr}}^{\mathrm{\ensuremath{-}}}$n(${5\mathrm{s}}^{2}

5p

{\mathrm{}}^{2}$P) ion have been measured by means of the laser photodetachment threshold technique combined with state-selective detection of neutral atoms using resonant ionization spectroscopy. We find binding energies of 32.17\ifmmode\pm\else\textpm\fi{}0.03 meV (J=3/2) and 52.06\ifmmode\pm\else\textpm\fi{}0.06 meV (J=1/2), yielding a fine-structure splitting of 19.89\ifmmode\pm\else\textpm\fi{}0.07 meV. This represents an improvement of two orders of magnitude compared to the recent data based on a combination of laser photodetachment and accelerator mass spectroscopy [D. Berkovits et al., Phys. Rev. Lett. 75, 414 (1995)].

{3p}^{5}4s{}^{3}{P}_{2}^{o}

state of neutral argon. Our calculations, based on many-body perturbation theory, yield a binding energy of 24.9 meV. As a test of the present computational method, we also include the results of a comparative study of ${\mathrm{Ca}}^{\ensuremath{-}}$.

{\mathrm{p}}_{1\mathrm{/}2}

components. This procedure yields fine-structure intervals in excellent agreement with experiment for ${\mathrm{Ca}}^{\mathrm{\ensuremath{-}}}$, ${\mathrm{Sr}}^{\mathrm{\ensuremath{-}}}$, and ${\mathrm{Ba}}^{\mathrm{\ensuremath{-}}}$, and allows us to predict that in ${\mathrm{Ra}}^{\mathrm{\ensuremath{-}}}$ the

{\mathrm{p}}_{1\mathrm{/}2}

state is bound by 100 meV, and

{\mathrm{p}}_{3\mathrm{/}2}

is a resonance at 16 meV in the continuum.

3d

{)}^{2}

D and (4s4

{p}^{2}$

{)}^{2}

D states of ${\mathrm{Ca}}^{\mathrm{\ensuremath{-}}}$. This interpretation is supported by ab initio configuration-interaction calculations and is consistent with previously unassigned structure observed in the photodetachment cross section.

p

-wave transition from the

{5s}^{2}5p^{2}P

ground state in ${\mathrm{Sr}}^{\ensuremath{-}}$ to the

5s5p^{3}P

state in neutral Sr. The measurement was made with a new technique combining the tunable laser photodetachment threshold method with accelerator mass spectrometry. We determine for the first time the electron affinity of Sr to be $48\ifmmode\pm\else\textpm\fi{}6\mathrm{meV}$, much smaller than predicted in recent calculations. The

^{2}P_{1/2}

^{2}P_{3/2}

fine splitting of the ${\mathrm{Sr}}^{\ensuremath{-}}$ ground state is estimated to be $26\ifmmode\pm\else\textpm\fi{}8\mathrm{meV}$.

Relative yields of

{\mathrm{Ca}}^{+}

and ${\mathrm{Ca}}^{\mathrm{\ensuremath{-}}}$ ions from thermal-energy collisions between highly excited

{\mathrm{Ca}}^{\mathrm{*}}

4snd

^{1}

D Rydberg atoms and Ca ground-state atoms are measured as a function of n. The collisions take place within an effusive Ca atomic beam. The cross section for a collision resulting in a bound ${\mathrm{Ca}}^{\mathrm{\ensuremath{-}}}$ and a ground-state

{\mathrm{Ca}}^{+}

is expected to be large when the binding energy of the excited Rydberg state nearly matches the electron affinity of Ca. We observe a large increase in positive and negative ions for n=25 only. This result strongly suggests that the binding energy of ${\mathrm{Ca}}^{\mathrm{\ensuremath{-}}}$ is 24\ifmmode\pm\else\textpm\fi{}1.4 meV.