Journal of Physics B Atomic Molecular and Optical Physics

Three-photon ionization of Ca

Roman S. Dygdała, Krzysztof Karasek, F. Giammanco, Jacek Kobus, Anna M. Zawadzka, Andrzej Raczyński, Jarosław Zaremba, Marek Zieliński

Published May 28, 1998• 17 citations

Publisher

Abstract

The two- and three-photon resonant ionization of Ca has been studied. Calcium atoms in the thermal atomic beam were ionized from the ground state by three-photon absorption. The ion signals exhibited resonances attributed to the two-photon transition and three-photon transitions due to , , and , autoionizing states. A simple theoretical model was used to reproduce the main features of the observed spectra due to the two-photon resonant ionization.

DOI: 10.1088/0953-4075/31/10/015

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Journal of Physics B Atomic Molecular and Optical Physics

Three-photon ionization of Ca

Roman S. Dygdała, Krzysztof Karasek, F. Giammanco, Jacek Kobus, Anna M. Zawadzka, Andrzej Raczyński, Jarosław Zaremba, Marek Zieliński

Published May 28, 1998• 17 citations

Publisher

Abstract

DOI: 10.1088/0953-4075/31/10/015

Related papers

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Anna M. Zawadzka, Roman S. Dygdała, Andrzej Raczyński +2 more

In the present study we have investigated three-photon ionization in Ca in which autoionizing states are engaged. The two-photon resonant process (from the Ca ground state 4s 2 1 S 0 ) occurred through or at least in the vicinity of one of the following states: 4s4d 1 D 2 , 4p 2 3 P 2 , 4s6s 1 S 0 , 4p 2 1 D 2 and 4p 2 1 S 0 , with the third photon either reaching the continuum directly or one of the autoionizing states. The three-photon resonant transitions to 3d m p, m f: 1 P 1 , 3 P 1 and 3 D 1 autoionizing states for m up to 21 have been observed. Some of the autoionizing resonances which we have found had not been observed before in a high-resolution one-photon absorption experiment (for J = 1) and in multiphoton experiments (for J = 3). We have compared the ionization signal as a function of the laser detuning and the laser intensity with theoretical curves obtained within a simple model (three-level atom + one-mode laser field). This gives information about the order of magnitude of the three-photon ionization probability through autoionizing states.In the present study we have investigated three-photon ionization in Ca in which autoionizing states are engaged. The two-photon resonant process (from the Ca ground state 4s 2 1 S 0 ) occurred through or at least in the vicinity of one of the following states: 4s4d 1 D 2 , 4p 2 3 P 2 , 4s6s 1 S 0 , 4p 2 1 D 2 and 4p 2 1 S 0 , with the third photon either reaching the continuum directly or one of the autoionizing states. The three-photon resonant transitions to 3d m p, m f: 1 P 1 , 3 P 1 and 3 D 1 autoionizing states for m up to 21 have been observed. Some of the autoionizing resonances which we have found had not been observed before in a high-resolution one-photon absorption experiment (for J = 1) and in multiphoton experiments (for J = 3). We have compared the ionization signal as a function of the laser detuning and the laser intensity with theoretical curves obtained within a simple model (three-level atom + one-mode laser field). This gives information about the order of magnitude of the three-photon ionization probability through autoionizing states.

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Harold K. Haugen, Henrik Stapelfeldt

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Physical Review AFeb 1, 199212 citations

We theoretically study multiphoton ionization of the Ca atom irradiated by the second (photon energy

3.1

eV) and third (photon energy 4.65 eV) harmonics of Ti:sapphire laser pulses (photon energy

1.55

eV). Because of the dense energy level structure the second and third harmonics of a Ti:sapphire laser are nearly single-photon resonant with the

4s4p

{}^{1}{P}^{o}

and

4s5p

{}^{1}{P}^{o}

states, respectively. Although two-photon ionization takes place through the near-resonant intermediate states with the same symmetry in both cases, it turns out that there are significant differences between them. The photoelectron energy spectra exhibit the absence or presence of substructures. More interestingly, the photoelectron angular distributions clearly show that the main contribution to the ionization processes by the third harmonic arises from the far-off-resonant

4s4p

{}^{1}{P}^{o}

state rather than the near-resonant

4s5p

{}^{1}{P}^{o}

state. These findings can be attributed to the fact that the dipole moment for the

4{s}^{2}

${}^{1}{S}^{e}\ensuremath{-}4s5p$

{}^{1}{P}^{o}

transition is much smaller than that for the

4{s}^{2}

${}^{1}{S}^{e}\ensuremath{-}4s4p$

{}^{1}{P}^{o}

transition.

{\mathrm{Ca}}^{+}

(4p),

{\mathrm{Ca}}^{+}

(5s), and

{\mathrm{Ca}}^{+}

(4d), and from

{\mathrm{Sr}}^{+}

(5p) and

{\mathrm{Sr}}^{+}

(6s). The contribution of the highly excited states was found to be favored under short-pulse (35-ps) irradiation.