Applications of the Schwinger variational principle to electron-molecule collisions and molecular photoionization

Lucchese, Robert R.; Takatsuka, Kazuo; McKoy, Vincent

doi:10.1016/0370-1573(86)90147-x

Cited by 246 publications

(131 citation statements)

References 117 publications

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“…To further examine these multiplet-specific effects, we have studied the photoionization cross sections and photoelectron angular distributions for the 3ug level of0 2 using Hartree-Fock photoelectron orbitals obtained with the iterative Schwinger method. 16 Our results for these cross sections agree well with those of Winstead et a/. 6 and, furthermore, show large differences in the multiplet-specific photoelectron angular distributions.…”

Section: Introductionsupporting

confidence: 91%

“…( 3) were obtained using the iterative Schwinger variational method, discussed extensively elsewhere. 16 • 17 To solve the Lippmann-Schwinger equations for the continuum orbital associated with the nonlocal molecular ion potential of Eq. ( 3), the scattering potential is approximated by a separable form, ij where the matrix U -1 is the inverse of the matrix with elements Uu = (a; I U laj) and the a;'s are discrete basis functions (see Table II).…”

Section: Calculationsmentioning

confidence: 99%

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Multiplet-specific shape resonant features in 3σg photoionization of O2

Braunstein

McKoy

Smith

1989

The Journal of Chemical Physics

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We report multiplet-specific photoionization cross sections and photoelectron angular distributions for the 3ug orbital of 0 2 leading to the b 4 l:g-and B 2 l:g-ion states obtained using Hartree-Fock photoelectron orbitals. These cross sections show significant nonstatistical behavior at low photoelectron energies which arises from the sensitivity of the kuu shape resonance to the exchange potentials ofthese two molecular ions. Specifically, the oscillator strength associated with the shape resonance in the B 2 l:g-cross section is shifted to lower energy compared to that of the b 4 l:g-cross section. This shift gives rise to a quartet to doublet cross section ratio of more than 15:1 near threshold. These effects are difficult to assess in the measured cross sections due to the presence of strong autoionization features. Significant multiplet dependence is also seen in the calculated photoelectron angular distributions.

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Section: Introductionsupporting

confidence: 91%

Section: Calculationsmentioning

confidence: 99%

Multiplet-specific shape resonant features in 3σg photoionization of O2

Braunstein

McKoy

Smith

1989

The Journal of Chemical Physics

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“…To obtain the photoelectron orbitals we have used an iterative procedure, based on the Schwinger variational principle, 77,78 to solve the Lippmann-Schwinger equation associated with Eq. ͑14͒.…”

Section: B Final State Wave Functionsmentioning

confidence: 99%

“…The calculations required for comparison with electron impact data at high energies are straightforward and are very closely related to the photon impact calculations. 77 Modern advances in the theory of fundamental scattering dynamics can enable electron scattering to fulfill the role originally envisioned by previous investigators 86,87,[95][96][97][98][99] as a means of diagnosing molecular beam expansion characteristics. We will describe the application of photon and electron impact ionization as a diagnostic tool in detail elsewhere.…”

Section: Implications For Electron Beam Diagnostics Of Supersonic mentioning

confidence: 99%

Photoion rotational distributions from near-threshold to deep in the continuum

Poliakoff

Choi

Rao

et al. 1995

The Journal of Chemical Physics

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We present the first measurements of ion rotational distributions for photoionization over an extended range ͓0рE K р200 eV for N 2 ͑2 u Ϫ1 ͒ and 3рE K р125 eV for CO ͑4 Ϫ1 ͔͒. The N 2 ion rotational distributions are seen to change dramatically over this energy range, indicating that characteristically molecular behavior of the photoelectron persists far from ionization threshold. In addition, the N 2 and CO results show a strikingly different dependence on energy. Although differences are expected due to the absence of a center of symmetry in CO, detailed calculations reveal that this behavior arises from the presence of Cooper minima in the 2 u →k g continuum in the case of N 2 and from an f -wave shape resonance in the 4 →k channel in CO. Agreement between measured and calculated ion rotational distributions is excellent. The N 2 results are also compared with electron bombardment ionization data. This comparison demonstrates that previous interpretations of electron bombardment data are prone to errors.

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“…For instance, the multichannel Schwinger configuration-interaction method (MC-SCI) of Lucchese and co-workers [33][34][35] has been shown to provide accurate predictions of molecular-frame photoemission observables measured for a series of molecular targets [20][21][22]30,31]. Density functional theory (DFT) calculations have also been conducted and predict richly structured measured angular distributions from fixed-in-space small polyatomic molecules [36], with recent developments involving time-dependent DFT [37].…”

Section: Theoretical Methodsmentioning

confidence: 99%

Circular dichroism in molecular-frame photoelectron angular distributions in the dissociative photoionization ofH2andD2molecules

et al. 2014

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The presence of net circular dichroism in the photoionization of nonchiral homonuclear molecules has been put in evidence recently through the measurement of molecular-frame photoelectron angular distributions in dissociative photoionization of H 2 [Dowek et al., Phys. Rev. Lett. 104, 233003 (2010)]. In this work we present a detailed study of circular dichroism in the photoelectron angular distributions of H 2 and D 2 molecules, oriented perpendicularly to the propagation vector of the circularly polarized light, at different photon energies (20, 27, and 32.5 eV). Circular dichroism in the angular distributions at 20 and to a large extent 27 eV exhibits the usual pattern in which inversion symmetry is preserved. In contrast, at 32.5 eV, the inversion symmetry breaks down, which eventually leads to total circular dichroism after integration over the polar emission angle. Time-dependent ab initio calculations support and explain the observed results for H 2 in terms of quantum interferences between direct photoionization and delayed autoionization from the Q 1 and Q 2 doubly excited states into ionic states (1sσ g and 2pσ u ) of different inversion symmetry. Nevertheless, for D 2 at 32.5 eV, there is a particular case where theory and experiment disagree in the magnitude of the symmetry breaking: when D + ions are produced with an energy of around 5 eV. This reflects the subleties associated to such simple molecules when exposed to this fine scrutiny.

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Applications of the Schwinger variational principle to electron-molecule collisions and molecular photoionization

Cited by 246 publications

References 117 publications

Multiplet-specific shape resonant features in 3σg photoionization of O2

Multiplet-specific shape resonant features in 3σg photoionization of O2

Photoion rotational distributions from near-threshold to deep in the continuum

Circular dichroism in molecular-frame photoelectron angular distributions in the dissociative photoionization ofH2andD2molecules

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