Dipole and nondipole photoionization of molecular hydrogen

Abstract

We describe a theoretical approach to molecular photoionization that includes first-order corrections to the dipole approximation. The theoretical formalism is presented and applied to photoionization of H 2 over the 20-to 180-eV photon energy range. The angle-integrated cross section σ , the electric dipole anisotropy parameter β e , the molecular alignment anisotropy parameter β m , and the first-order nondipole asymmetry parameters γ and δ were calculated within the single-channel, static-exchange approximation. The calculated parameters are compared with previous measurements of σ and β m and the present measurements of β e and γ + 3δ. The dipole and nondipole angular distribution parameters were determined simultaneously using an efficient, multiangle measurement technique. Good overall agreement is observed between the magnitudes and spectral variations of the calculated and measured parameters. The nondipole asymmetries of He 1s and Ne 2p photoelectrons were also measured in the course of this work.

Perturbative and nonperturbative photoionization of H2 and H2O using the molecular R<

“…Still, the agreement is very good, particularly with the experimental data from Ref. [50], except for the 30-35 eV region, where some resonant peaks are clearly visible in the fixed-nuclei (equilibrium geometry) results.…”

“…3. Fixed-nuclei (equilibrium) and vibrationally averaged effective dipole asymmetry parameter β 2 for one-photon ionization of H 2 compared with experiments of Marr et al [47], Southworth et al [48], Parr et al [49], and Zimmermann et al [50] and an earlier stationary R-matrix calculation by Tennyson et al [51] with a different molecular model. et al [44].…”

“…In Fig. 2 the RMT cross sections shown were obtained for very long pulses (greater than 100 cycles); for the ATZ basis set we tested the use of Marr et al [47] Southworth et al [48] Tennyson et al [51] Parr et al [49] Zimmermann et al [50] FIG. 3.…”

Photon-momentum transfer in diatomic molecules: An ab initio study

“…Due to the progress of the experimental technologies and methodologies, the nondipole effects in atoms ionized by the infrared and mid-infrared lasers have been observed recently [7,8]. For a long time, the nondipole effects in photoelectron angular distributions from atoms and molecules have been investigated theoretically [9][10][11][12][13][14][15] and experimentally [16][17][18]. By integrating over those asymmetric electron distributions, one can get a net momentum of photoelectron along the direction of the laser propagation [1,7,8], which comes from the linear photon momentum partition between the photoelectron and the residual ion.…”

Theoretical description of the ionization processes with a discrete basis set representation of the electronic continuum

“…Their method includes a way of optimizing the GTO set by expressing the functional for the frequency dependent polarizability as a function of the orbital exponents and seeking its stationary point. Let us also note the recent discussion of Zimmermann et al [90] on the effect of non-dipole photoionization of the hydrogen molecule.…”