We report the measurement of the two-photon detachment spectrum of the $^{1}D^{e}$ resonance of ${\mathrm{H}}^{\ensuremath{-}}$ just below the $n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2$ threshold. The excess photon detachment resonance fits a Fano profile with energy 10.872(2) eV (relative to ${\mathrm{H}}^{\ensuremath{-}}$ ground state), a width of 0.0105(10) eV, and a shape parameter of $\ensuremath{-}8(2)$. To our knowledge, this describes the first time direct multiphoton excitation of a resonance has been observed in any negative atomic ion.We report the measurement of the two-photon detachment spectrum of the $^{1}D^{e}$ resonance of ${\mathrm{H}}^{\ensuremath{-}}$ just below the $n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2$ threshold. The excess photon detachment resonance fits a Fano profile with energy 10.872(2) eV (relative to ${\mathrm{H}}^{\ensuremath{-}}$ ground state), a width of 0.0105(10) eV, and a shape parameter of $\ensuremath{-}8(2)$. To our knowledge, this describes the first time direct multiphoton excitation of a resonance has been observed in any negative atomic ion.

Physical Review LettersOct 16, 199544 citations

Polarization effects in two-colour photodetachment of negative ions

Wilhelm Becker, Li-E Li, John K. McIver

Two-colour photodetachment of a negative ion modelled by a three-dimensional delta-function potential is theoretically investigated. The high-frequency low-intensity field is closely tuned to the detachment energy of the ion, the low-frequency high intensity field creates a ponderomotive potential of 2.6% of the detachment energy and at the same time sidebands. The two fields are circularly polarized with either equal or opposite polarizations. In accordance with the Wigner threshold law, for equal and opposite polarizations, the sideband-induced thresholds are above or below the one-photon detachment threshold, respectively. The one-photon threshold is markedly visible for opposite polarizations at the position shifted by the full ponderomotive potential. For equal polarizations and low frequencies it is not noticeable at all.Two-colour photodetachment of a negative ion modelled by a three-dimensional delta-function potential is theoretically investigated. The high-frequency low-intensity field is closely tuned to the detachment energy of the ion, the low-frequency high intensity field creates a ponderomotive potential of 2.6% of the detachment energy and at the same time sidebands. The two fields are circularly polarized with either equal or opposite polarizations. In accordance with the Wigner threshold law, for equal and opposite polarizations, the sideband-induced thresholds are above or below the one-photon detachment threshold, respectively. The one-photon threshold is markedly visible for opposite polarizations at the position shifted by the full ponderomotive potential. For equal polarizations and low frequencies it is not noticeable at all.

Journal of Physics B Atomic Molecular and Optical PhysicsNov 28, 199010 citations

We report the measurement of the two-photon detachment spectrum of the

^{1}D^{e}

resonance of ${\mathrm{H}}^{\ensuremath{-}}$ just below the

n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2

threshold. The excess photon detachment resonance fits a Fano profile with energy 10.872(2) eV (relative to ${\mathrm{H}}^{\ensuremath{-}}$ ground state), a width of 0.0105(10) eV, and a shape parameter of $\ensuremath{-}8(2)$. To our knowledge, this describes the first time direct multiphoton excitation of a resonance has been observed in any negative atomic ion.