Interferences from Fast Electron Emission in Molecular Photoionization

Fernández, J.; Fojón, O A; Palacios, Alicia; Martín, Fernando

doi:10.1103/physrevlett.98.043005

Cited by 109 publications

(111 citation statements)

References 23 publications

(28 reference statements)

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“…Nevertheless, the RPA/RCHF methods lead somehow to sharper minima, which is the consequence of not including the nuclear motion in their calculations. A similar effect has been reported in H 2 photoionization 80,154,155 .…”

Section: Core Photoionization At High Photon Energiessupporting

confidence: 67%

“…The formula is only expected to work qualitatively at high enough k e , i.e., when the potential felt by the escaping electron is small compared to its kinetic energy, and it should work better for σ → σ than for σ → π transitions because, in the former, electrons mainly scape along the direction of the molecular axis (see Ref. 80,154,155 for a more detailed description in the case of the H 2 molecule). The effect is less pronounced in the CO partial wave contributions (see Figs.…”

Section: Core Photoionization At High Photon Energiesmentioning

confidence: 99%

“…Two of these phenomena, which lie at the heart of quantum mechanics, have been recently observed in vibrationally resolved photoelectron spectra from valence-shell orbitals 78 : (i) two-center coherent electron emission leading to Young's type double-slit interferences 79 and (ii) electron diffraction by the molecule's atomic centers. 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%

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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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Section: Core Photoionization At High Photon Energiessupporting

confidence: 67%

Section: Core Photoionization At High Photon Energiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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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“…The oscillatory term within brackets quantifies the interference effect (hereafter called Cohen-Fano, CF, interference). The beauty of such a simple expression is that it is proportional to the very general intensity pattern produced by two dipole antennas separated by a distance R e that radiate coherently (5). Eq.…”

mentioning

confidence: 99%

Direct observation of Young’s double-slit interferences in vibrationally resolved photoionization of diatomic molecules

Canton

Plésiat

Bozek

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

107

120

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Vibrationally resolved valence-shell photoionization spectra of H 2 , N 2 and CO have been measured in the photon energy range 20-300 eV using third-generation synchrotron radiation. Young's double-slit interferences lead to oscillations in the corresponding vibrational ratios, showing that the molecules behave as two-center electron-wave emitters and that the associated interferences leave their trace in the angle-integrated photoionization cross section. In contrast to previous work, the oscillations are directly observable in the experiment, thereby removing any possible ambiguity related to the introduction of external parameters or fitting functions. A straightforward extension of an original idea proposed by Cohen and Fano [Cohen HD, Fano U (1966) photoelectron spectroscopy | molecular spectroscopy | molecular ionization | density functional theory | quantum chemistry T he recognition of wave-particle duality, resolving centuries of scientific debate, is nowadays considered as a milestone in the development of Quantum Mechanics. This revolutionary concept has been repeatedly demonstrated in variations of Young's double-slit experiment, where a beam of massive particles, from electrons (1) to fullerenes (2), with momentum p e , passing through two slits separated by a distance comparable to their associated de Broglie wavelength (λ e ¼ h∕p e ) displays temporal and spatial coherence evidenced through interferogram fringes (3). In the 1960's, Cohen and Fano (4) conjectured the possibility to realize the double-slit experiment on the microscopic length scale by photoionizing a diatomic molecule, where the source of free electrons is delocalized over two atomic centers. A sketch of the interference expected from the coherent emission of the two centers is shown in Fig. 1.Coherence is observable when the electron-wave length λ e is of the order of R e , or equivalently, when the photon energy hν is of the order of I p þ h 2 ∕ð2m e R 2 e Þ, where R e is the internuclear distance at equilibrium, m e is the electron mass, and I p is the vertical ionization potential. These energies correspond to incoming photons of a few hundred eV, i.e., to vacuum or extreme ultraviolet radiation. Fingerprints of this coherent emission can be found in the total photoionization cross section, which in the case of a homonuclear diatomic molecule is approximately given by the formulawhere σ 0 is an atomic photoionization cross section (for an effective charge Z eff ) and k e ¼ 2π∕λ e is the electron-wave vector. The oscillatory term within brackets quantifies the interference effect (hereafter called Cohen-Fano, CF, interference). The beauty of such a simple expression is that it is proportional to the very general intensity pattern produced by two dipole antennas separated by a distance R e that radiate coherently (5). Eq. 1 is obtained by assuming that the ionized molecular orbital ψ can be expressed by a linear combination of atomic orbitals (LCAO):where 1s A and 1s B are identical 1s atomic orbitals centered on atoms A and B of...

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“…Fig. 1 presents the results of recent theoretical calculations [70] including the full dimensionality of the electronic and vibrational motions. Panels (a) show the integrated (in electron energy and solid angle) cross section as a function of photon energy for polarized light parallel (Σ + u symmetry) and perpendicular (Π u symmetry) to the molecular axis.…”

Section: Photoionization Of H 2 At High Photon Energiesmentioning

confidence: 99%

Molecular ionization and dissociation using synchrotron radiation and ultrashort laser pulses

Martín¹

2007

J. Phys.: Conf. Ser.

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Abstract. An overview of recent theoretical progress to accurately describe non dissociative and dissociative ionization of molecules exposed to synchrotron radiation and ultrashort uv/xuv laser pulses is presented. The success of recent theoretical approaches rely on their ability to account for both the electronic and nuclear degrees of freedom. This is essential to describe the delicate interplay between the electronic motion and the molecule's vibration, especially in those cases where ionization occurs in a time scale comparable to that of the vibrational motion. Some of the most successful applications and the new physics that has emerged by comparing with recent kinematically complete experiments on H2 and D2 will be discussed. IntroductionMolecular ionization is one of the most elementary processes that occurs in the upper atmosphere [1] and in interstellar molecular clouds [2]. Since in molecules the absorbed energy is shared between electronic and nuclear degrees of freedom, the remaining molecular ion can be left in an excited vibrational or dissociative state. This is at variance with atomic ionization where the energy is entirely absorbed by the electrons. In early pictures of molecular ionization, the nuclear motion was either ignored or described in terms of the Franck-Condon (FC) approximation, in which electronic processes occurring at the equilibrium position of the nuclei are weighted by the squared overlap between the initial and final vibrational states. With the advent of kinematically complete experiments [3,4], in which the momenta of all charged particles is determined, new phenomena with an intrinsic molecular origin have been discovered (see, e.g., [5][6][7][8][9][10][11]). Also the above pictures have been revealed to be incomplete. In this manuscript, the important role of nuclear dynamics in molecular ionization produced by synchrotron radiation and ultrashort pulses will be demonstrated by means of recent ab initio theoretical calculations that account for all electronic and vibrational degrees of freedom.In particular, recent results for electron angular distributions from fixed-in-space molecules will be analyzed and compared with kinematically complete photoionization experiments using synchrotron radiation. These include double and single photoionization of H 2 (D 2 ). The range of excess photon energies considered goes from a few to several hundreds of eV. Also, multiphoton ionization of molecules by vuv ultrashort pulses will be discussed. In particular, the new physics that can be expected by varying pulse duration and intensity will be analyzed.

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Interferences from Fast Electron Emission in Molecular Photoionization

Cited by 109 publications

References 23 publications

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

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

Direct observation of Young’s double-slit interferences in vibrationally resolved photoionization of diatomic molecules

Molecular ionization and dissociation using synchrotron radiation and ultrashort laser pulses

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