Shape resonances in the photoionization of N2O

Braunstein, M.; McKoy, Vincent

doi:10.1063/1.453620

Cited by 30 publications

(22 citation statements)

References 18 publications

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“…7 the experimental cross section and asymmetry parameters of the satellite lines are shown. These have been obtained by using some simplifying assumptions in the line-shape analysis: (i) the satellite band S3 is assumed to consist of only one (broad) line located at E"i = 16 It is evident that for photon energies above 340 eV, the relative cross sections of the three main satellites approach a constant value in agreement with spectra taken in the sudden limit. Below this energy, So exhibits a maximum in intensity at -328 eV that falls dramatically for energies h v& 325 eV.…”

Section: Satellitesmentioning

confidence: 99%

Shape resonances and multielectron effects in the core-level photoionization ofCO2

et al. 1995

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The partial photoionization cross sections and angular distributions of the C 1s ' and 0 1s ' singlehole states of CO2 have been measured with high precision near threshold. The 4o. "shape resonance is well reproduced in the 1s single-hole cross sections, but strong site-specific effects are observed with respect to both its energy and intensity. A striking feature of the present data is the presence of fine structure in the 1s single-hole cross sections o. » due to multielectron excitations: virtually all spectral details in the total 1s cross sections o.&, are also present in o. sH implying that multielectron excitations couple strongly to the underlying 1s continuum. The decay dynamics of the double-excitation feature at 303.5 eV in the C 1s cross section of CO2 have been characterized by Auger spectroscopy. Partial cross sections and angular distributions have also been measured for the first group of strong shake-up satellites in the C 1s photoelectron spectrum. Similar to the C 1s ionization of CO, a strong enhancement of intensity near threshold is observed for some satellite channels as well as the occurrence of features that are not present in the sudden limit. The latter are attributed to conjugate shake-up.PACS number(s): 33.80.Eh, 33.60.Fy I. INTRQDUCTIGNA considerable body of experimental and theoretical work on photoabsorption and photoionization cross sections has shown that resonances and multielectron effects are commonly encountered in core-level excitation of small molecules. In some studies these features have been carefully characterized and provide models for the interpretation of similar efFects in larger molecules [1,2]. The current upsurge of interest in such K-shell properties is due to recently improved instrumentation, in particular high-resolution monochromator s in combination with undulator sources, for absorption and photoelectron spectroscopy experiments, e.g. , [3 -6]. These allow detailed examination of the energetics and dynamics of core-level photoionization.The excitation of a core electron into an unoccupied bound molecular orbital or the continuum is generally accomplished by a strong relaxation of the remaining system of charges. Provided that sufhcient energy is available from the absorbed photon, there is a relatively high probability that a valence electron and vibrations are excited simultaneously with the core electron, giving rise to shake-up satellites in the photoelectron spectra [7 -10] and to vibrational structure in both photoabsorption [3 -5] and photoemission spectra [6,11]. Transitions to unoccupied states accompanied by shake-up often produce characteristic features in the continuum just below the onset of the shake-up satellites seen in the photoelectron spectra and have been referred to as double excitations. In the same energy region, i.e. , within the erst tens 'Present address: Max-Planck-Arbeitsgruppe "Rontgenbeugung, " Hausvogteiplatz 5-7, 10117Berlin, Germany. Present address: Hamburger Synchrotronstrahlungslabor at DESY, Notkestralje 85, 22603 Hamb...

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Section: Satellitesmentioning

confidence: 99%

Shape resonances and multielectron effects in the core-level photoionization ofCO2

et al. 1995

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“…[22][23][24][25] For polyatomic systems, however, there is comparatively little work on vibrationally state-resolved valence shell photoionization, and the current work provides qualitatively new material to such studies. Research on polyatomic systems have been shown to address novel issues, as experiment 32,42 and theory 43,44 demonstrated that vibrationally mode-specific effects were exhibited in N 2 O 7 Ϫ1 photoionization. This idea was similarly applied to CS 2 .…”

Section: B Connections To Related Spectroscopiesmentioning

confidence: 99%

Excitation of the symmetry forbidden bending mode in molecular photoionization

Miller

Poliakoff

Miller

et al. 2001

The Journal of Chemical Physics

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We present results on the energy dependence of the vibrational branching ratio for the bending mode in CO 2 3 u Ϫ1 photoionization. Specifically, we determine the v ϩ ϭ(0,1,0)/v ϩ ϭ(0,0,0) intensity ratio by detecting dispersed fluorescence from the electronically excited photoions. The results exhibit large deviations over a very wide energy range, 18Ͻh exc Ͻ190 eV. Production of the v ϩ ϭ(0,1,0) level of the ion from the v 0 ϭ(0,0,0) ground state is forbidden by symmetry, and while observations of such features are well established in photoelectron spectroscopy, their appearance is normally ascribed to vibronic coupling in the ionic hole state. In this case, we find that such explanations fail to account for the energy dependence of the branching ratio. These deviations indicate that the continuum photoelectron participates in transferring oscillator strength to the nominally forbidden vibrational transition. A theoretical framework is developed for interpreting the experimental data, and Schwinger variational calculations are performed. These calculations demonstrate that the continuum electron is responsible for the observation of the excited bending mode as well as its energy dependence. This is an intrachannel effect that is best described as photoelectron-induced vibronic symmetry breaking. This appears to be a general phenomenon, and it may be useful in illuminating connections between bond angle and photoionization spectroscopies. The magnitude of these deviations display the utility of vibrationally resolved studies, and the extent over which these changes occur underscores the necessity of broad range studies to elucidate slowly varying characteristics in photoionization continua.

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“…First, polarization data are useful for interpreting features in the partial photoionization cross section curves, and in the case of N 2 O 7 Ϫ1 photoionization, there are two peaks. [13][14][15][16] There is a relatively sharp feature near threshold (h exc Ϸ17.5 eV) which has been assigned as a 7→k shape resonance, and there is consensus on this interpretation. [14][15][16][17] However, there is another peak at h exc Ϸ34 eV, and while it has been predicted that a weak 7→k shape resonance occurs near this energy, calculations imply that most of the oscillator strength is due to a nonresonant 7→k contribution.…”

Section: Introductionmentioning

confidence: 99%

“…[13][14][15][16] There is a relatively sharp feature near threshold (h exc Ϸ17.5 eV) which has been assigned as a 7→k shape resonance, and there is consensus on this interpretation. [14][15][16][17] However, there is another peak at h exc Ϸ34 eV, and while it has been predicted that a weak 7→k shape resonance occurs near this energy, calculations imply that most of the oscillator strength is due to a nonresonant 7→k contribution. 15,16 The current study allows us to investigate the ''parentage'' of these peaks by quantifying the relative contributions of the underlying continua.…”

Section: Introductionmentioning

confidence: 99%

“…[14][15][16][17] However, there is another peak at h exc Ϸ34 eV, and while it has been predicted that a weak 7→k shape resonance occurs near this energy, calculations imply that most of the oscillator strength is due to a nonresonant 7→k contribution. 15,16 The current study allows us to investigate the ''parentage'' of these peaks by quantifying the relative contributions of the underlying continua. A second motivation is that recent studies on CO ϩ (B 2 ⌺ ϩ ) 18 and N 2 ϩ (B 2 ⌺ u ϩ ) 19 showed that the photoions retained significant alignment even at high photon energies, which was quite surprising.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Global energy dependence of N2O+(A 2Σ+) photoion alignment

Das

Poliakoff

1997

The Journal of Chemical Physics

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Articles you may be interested inNO+ formation pathways in dissociation of N2O+ ions at the C2Σ+ state revealed from threshold photoelectron-photoion coincidence velocity imaging J. Chem. Phys. 134, 054312 (2011); 10.1063/1.3549130 Anisotropy of the angular distribution of fragment ions in dissociative double photoionization of N 2 O molecules in the 30 -50 eV energy rangeWe present experimental results for the alignment of N 2 O ϩ (A 2 ⌺ ϩ ) photoions over an extended energy range (16.4рh exc р240 eV). The polarization of the N 2 O ϩ (A 2 ⌺ ϩ →X 2 ⌸) fluorescence is used to interpret the oscillator strength distributions for normally unresolved degenerate ionization channels. The results clearly show the influence of a near-threshold 7→k shape resonance, and help to clarify the results of previous fluorescence and photoelectron studies. At high photon energies, the photoelectrons are not favored to exit via a particular channel, in contrast to recent results on N 2 and CO, where photoelectrons are ejected preferentially via the k channel and the photoions retain significant alignment even at the highest measurable energies. These results demonstrate that even well above threshold the spectral dependence of the alignment ͑i.e., polarization͒ is very sensitive to the molecular environment for photoejection.

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Shape resonances in the photoionization of N2O

Cited by 30 publications

References 18 publications

Shape resonances and multielectron effects in the core-level photoionization ofCO2

Shape resonances and multielectron effects in the core-level photoionization ofCO2

Excitation of the symmetry forbidden bending mode in molecular photoionization

Global energy dependence of N2O+(A 2Σ+) photoion alignment

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