Shape-resonance-induced non-Franck-Condon vibrational intensities in 3 σ<sub>g</sub>photoionisation of N<sub>2</sub>

West, John B.; Parr, Albert C.; Cole, B. E.; Ederer, D. L.; Stockbauer, Roger; Dehmer, Joseph L.

doi:10.1088/0022-3700/13/3/004

Cited by 107 publications

(31 citation statements)

References 8 publications

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“…With this approximation to Vin Eq. (6), the solutions of this integral equation can be written as (8) where the matrix D -1 is the inverse of the matrix with elements…”

Section: Methods and Calculationsmentioning

confidence: 99%

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Shape resonances in the photoionization of N2O

Braunstein

McKoy

1987

The Journal of Chemical Physics

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We repo~ th~ results of studies of the cross sections and photoelectron asymmetry parameters for phot.otomzatlOn ~f the 7 0' level of N 2 0 using Hartree-Fock photoelectron continuum orbitals. These s~udt~ were ~O~lVa~ed by recent measurements which showed significant non-Franck-Condon vtbrattonal dtstnbutwns at low ph?toel~tron energies where previously only autoionizing resonances, but no shape resonance, had been Identified. Our results establish that there are two u shape resonances i? the 7u ionizati?n ~ontinu~m, a pronounced resonance at low photoelectron energies, and another at htgher energy whtch ts essentially obscured in the vibrationally unresolved cross sections. The sh~pe resonant st~cture t~at ~merges from these studies differs significantly from the predictions of previous model studies. Studies 10 progress reveal a rich and unusual dependence of these resonances on changes in internuclear distances.

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“…With this approximation to Vin Eq. (6), the solutions of this integral equation can be written as (8) where the matrix D -1 is the inverse of the matrix with elements…”

Section: Methods and Calculationsmentioning

confidence: 99%

“…Furthermore, these cross sections were calculated with the uniterated solutions ofEq. ( 8) for the photoelectron continuum orbitals. Calculations at several photon energies using more converged photoelectron orbitals obtained with our iterative procedure for solving Eq.…”

Section: Methods and Calculationsmentioning

confidence: 99%

Shape resonances in the photoionization of N2O

Braunstein

McKoy

1987

The Journal of Chemical Physics

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“…Thus, it possible to compare the rotational substructure between the two bands as a function of incident photon energy, analogous to a previous study on vibrationalrotational-electronic ͑V-R-E͒ correlations in 2 u Ϫ1 photoionization of N 2 . 37 It is well known that the effects of shape resonances are influenced by the bond length for diatomic systems, 69,70 so it is reasonable to inquire if the rotational substructure would be affected, particularly in the lower energy region where the shape resonant effects are dominant. This comparison has been generated, and the results are shown in Fig.…”

Section: A Typical Comentioning

confidence: 99%

Rotationally resolved photoionization: Influence of the 4σ→kσ shape resonance on CO+(B 2Σ+) rotational distributions

Farquar

Miller

Poliakoff

et al. 2001

The Journal of Chemical Physics

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We present experimental and theoretical results on rotational distributions of CO ϩ (B 2 ⌺ ϩ ) photoions. Rotational distributions were determined for both the v ϩ ϭ0 and v ϩ ϭ1 vibrational levels following photoionization of cold (T 0 Ϸ9 K) neutral CO target molecules. Data were generated using dispersed ionic fluorescence over a wide range of photoelectron kinetic energies, 0рE k р120 eV, which allows one to interrogate the ionization dynamics. This wide spectral coverage permits illustrative comparisons with theory, and calculated spectra are presented to interpret the data. In particular, the comparison between theory and experiment serves to identify the strong continuum resonant enhancement at h exc Ϸ35 eV in the lϭ3 partial wave of the 4→k ionization channel, as this feature has profound effects on the ion rotational distributions over a wide range of energy. Second, there are differences between the rotational substructure for the v ϩ ϭ0 and v ϩ ϭ1 vibrational levels. All of the experimentally observed features and trends are reproduced by theory, and the consequences of these comparisons are discussed.

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“…Previous examples result from resonant excitation, either autoionization [18] or shape resonance [16,17,19]. In these cases, the eigenphase sum goes through p, and the cross section goes through an extremum.…”

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confidence: 99%

Global Franck-Condon Breakdown Resulting from Cooper Minima

et al. 1996

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Using N 2 2s 21 u photoionization as an example, we present the first measurements and calculations of photoion vibrational distributions for an extended energy range (5 # E k # 230 eV). The results show a striking breakdown of the Franck-Condon approximation over a 100 eV range. We show that this coupling between vibrational and electronic motion arises from a dependence of Cooper minima on molecular bond length. Based on this mechanism, the effect is expected to be common for molecular systems. PACS numbers: 33.80.Eh, 33.50.Dq The energy dependence of vibrationally resolved partial cross sections is central in the interpretation of molecular photoionization and detachment data. A clear picture of vibrational aspects of photoionization is a prerequisite for interpreting intensities quantitatively [1], and consequently for extracting accurate ionic potential surfaces. As examples, note that vibrationally resolved photoelectron spectra are essential ingredients for probing the chemical transition state [2] and extracting the structure of atomic and molecular clusters [3]. In interpretations of photoionization and photodetachment spectra, it is usually assumed that the vibrational intensities are governed by the Franck-Condon (FC) approximation, and hence that the ratio of cross sections for alternative vibrational levels is constant with photon energy. In this Letter, we report the first observation of coupling between electronic and vibrational motion which is global in extent, extending over a range of more than 100 eV. With N 2 2s 21 u photoionization as an example, we show that the source of this Franck-Condon breakdown is a strong dependence of Cooper minima on internuclear separation over a broad energy range. Moreover, because of the underlying dynamics of the breakdown, this behavior is expected to be the rule rather than the exception in molecular photoionization. Viewed in a larger context, these results provide fundamental insights into the correlation between nuclear and electronic degrees of freedom.Cooper minima [4,5] are ubiquitous for atomic and molecular systems. They originate from a change in sign of the dipole matrix element as a function of photon energy, so that the matrix element goes through zero. For molecular systems, the effects of Cooper minima on photoelectron angular distributions are well documented [5]. However, the influence of cooper minima on molecular vibration over a wide spectral range has never been explored [6,7], and that is the topic of the current study. We show-both experimentally and theoretically-that the N 2 2s 21 uCooper minima are strongly R dependent, and that an important manifestation of this R dependence is a coupling between electronic and nuclear motion. This study demonstrates that Cooper minima can result in deviations from Franck-Condon behavior over a broader range than any previously studied mechanism (by more than an order of magnitude). In so doing, this study highlights the molecular character of the photoelectron dynamics, even for scattering ener...

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Shape-resonance-induced non-Franck-Condon vibrational intensities in 3 σ_gphotoionisation of N₂

Cited by 107 publications

References 8 publications

Shape resonances in the photoionization of N2O

Shape resonances in the photoionization of N2O

Rotationally resolved photoionization: Influence of the 4σ→kσ shape resonance on CO+(B 2Σ+) rotational distributions

Global Franck-Condon Breakdown Resulting from Cooper Minima

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Shape-resonance-induced non-Franck-Condon vibrational intensities in 3 σgphotoionisation of N2

Cited by 107 publications

References 8 publications

Shape resonances in the photoionization of N2O

Shape resonances in the photoionization of N2O

Rotationally resolved photoionization: Influence of the 4σ→kσ shape resonance on CO+(B 2Σ+) rotational distributions

Global Franck-Condon Breakdown Resulting from Cooper Minima

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Shape-resonance-induced non-Franck-Condon vibrational intensities in 3 σ_gphotoionisation of N₂