Interference in the Photo-Ionization of Molecules

Cohen, Howard D.; Fano, U.

doi:10.1103/physrev.150.30

Cited by 429 publications

(367 citation statements)

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“…Here the g and u states show also pronounced oscillations in their partial photoionization cross sections and even more pronounced oscillations in their photoelectron diffraction intensity behavior in the molecular frame. These oscillations which were predicted more than forty years ago by Cohen and Fano [9] have been experimentally corroborated since the last ten years only [10,11]. Regarding photoionization this was even more recently [12].…”

Section: Introduktionsupporting

confidence: 53%

Partial photoionization cross sections of C60 and C70: A gas versus adsorbed phase comparison

et al. 2010

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We have performed high resolution measurements of the photoelectrons emitted from the valence shell of C70, in the gas and adsorbed phase on a metal surface, in order to derive branching ratios and the partial photoionization cross sections of the two highest occupied molecular orbitals, HOMO and HOMO-1. The comparison between the two phases and the adsorbed phase shows an interesting and unexpected difference that can be attributed to a small orbital shift in solid C70. Density Functional Theory calculations within the Local Density Approximation (LDA) show good agreement for both data sets and give a plausible explanation for the observed difference. IntroduktionThe discovery of the family of carbon molecules dubbed the 'fullerenes' [1] and the breakthrough in their synthesis [2] have stimulated an extensive research activity in this field. The best known among the fullerenes is the C60 molecule, which consists of 60 carbon atoms arranged on a nearly spherical shell with the highest possible symmetry, point group Ih. Recently, we have studied some of its particularly interesting properties by photoelectron spectroscopy [3]. Our results revealed strong oscillations in the partial photoionization cross sections of the two highest occupied molecular orbitals, HOMO and HOMO-1, reflecting the molecular geometry and symmetry of the electronic charge distribution.These oscillations, which were for the first time discovered in solid C60 and interpreted as a solid state effect [4,5], were later also observed for free C60 molecules [6]. Their interpretation was basically interpreted within a standing wave model of the photoelectron wave in a box like potential [7] being extended to a jellium like potential in a subsequent experimental and theoretical study [8]. It is the spherical like structure of the C60 molecule which gives rise to shell like distribution of the delocalized carbon valence electrons. However, one may look to the problem also from the view point of symmetry. The valence hole states HOMO and HOMO-1 have different symmetry gerade (g) and ungerade (u), a situation which may be compared to homonuclear diatomic molecules. Here the g and u states show also pronounced oscillations in their partial photoionization cross sections and even more pronounced oscillations in their photoelectron diffraction intensity behavior in the molecular frame. These oscillations which were predicted more than forty years ago by Cohen and Fano [9] have been experimentally corroborated since the last ten years only [10,11]. Regarding photoionization this was even more recently [12]. The showcase example exhib-

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Section: Introduktionsupporting

confidence: 53%

Partial photoionization cross sections of C60 and C70: A gas versus adsorbed phase comparison

et al. 2010

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“…In these calculations, we have used the representation of the initial and final states proposed by Cohen and Fano [45]: The final state is described by a plane wave and the initial state by a linear combination of 1s orbitals corresponding to the actual nuclear charge Z = 1, but also to an R-dependent effective charge chosen to reproduce the exact ground-state potential energy curve. The ionization probability is obtained by weighting the square of the corresponding dipole matrix element with the ground-state nuclear probability density (reflection approximation [46]).…”

Section: Few-photon Absorptionmentioning

confidence: 99%

Molecular resolvent-operator method: Electronic and nuclear dynamics in strong-field ionization

et al. 2014

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We present an extension of the resolvent-operator method (ROM), originally designed for atomic systems, to extract differential photoelectron spectra (in photoelectron-and nuclear-kinetic energy) for diatomic molecules interacting with strong, ultrashort laser fields in the single active electron approximation. The method is applied to the study of H 2 + photodissociation and photoionization by femtosecond laser pulses in the XUV-IR frequency range. In particular, the method is tested (i) in the perturbative regime, for few-photon absorption and bound-bound electronic transitions, and (ii) in the strong-field regime, in which multiphoton absorption and tunneling are present. In the latter case, we show how the differential ROM allows one to track the transition between both regimes. We also analyze isotopic effects by comparing the dynamics of H 2 + and D 2 + ionization for different pulses.

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“…These processes are possible because, at high photon energy, the wavelength λ e of the ejected electron is comparable to or smaller than the size of the molecule 80,81 ; consequently, ejected electrons experience the same phenomena as normal wave do. As a result, oscillations in the photoelectron spectra are expected but they are barely observed in the total photoelectron spectra due to the rapid decrease of the corresponding cross section with photon energy 82 .…”

Section: Introductionmentioning

confidence: 99%

Vibrational branching ratios in the photoelectron spectra of N2 and CO: interference and diffraction effects

Plésiat

Decleva

Martín

2012

Phys. Chem. Chem. Phys.

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Esta es la versión de autor del artículo publicado en: This is an author produced version of a paper published in: We present a detailed account of existing theoretical methods specially designed to provide vibrationally resolved photoionization cross sections of simple molecules within the Born-Oppenheimer approximation, with emphasis on newly developed methods based on density functional theory. The performance of these methods is shown for the case of N 2 and CO photoionization. Particular attention is paid to the region of high photon energies, where the electron wavelength is comparable to the bond length and, therefore, two-center interferences and diffraction are expected to occur. As shown in a recent work [Canton et al., Proc. Natl. Acad. Sci., 2011, 108, 73027306], the main experimental difficulty, which is to extract the relatively small diffraction features from the rapidly decreasing cross section, can be easily overcome by determining ratios of vibrationally resolved photoelectron spectra and existing theoretical calculations. From these ratios, one can thus get direct information about the molecular geometry. In this work, results obtained in a wide range of photon energies and for many different molecular orbitals of N 2 and CO are discussed and compared with the available experimental measurements. From this comparison, limitations and further possible improvements of the existing theoretical methods are discussed. The new results presented in the manuscript confirm that the conclusions reported in the above reference are of general validity.

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Interference in the Photo-Ionization of Molecules

Cited by 429 publications

References 10 publications

Partial photoionization cross sections of C60 and C70: A gas versus adsorbed phase comparison

Partial photoionization cross sections of C60 and C70: A gas versus adsorbed phase comparison

Molecular resolvent-operator method: Electronic and nuclear dynamics in strong-field ionization

Vibrational branching ratios in the photoelectron spectra of N2 and CO: interference and diffraction effects

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