Yields and Time-of-Flight Spectra of Neutral High-Rydberg Fragments at the K Edges of the CO2 Molecule (original) (raw)
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Journal of Physics B: Atomic, Molecular and Optical Physics, 1996
Absolute differential cross sections for electron-impact excitation of Rydberg states of CO have been measured from threshold to 3.7 eV above threshold and for scattering angles between 20 • and 140 • . Measured excitation functions for the b 3 + , B 1 + and E 1 states are compared with cross sections calculated by the Schwinger multichannel method. The behaviour of the excitation functions for these states and for the j 3 + and C 1 + states is analysed in terms of negative-ion states. One of these resonances has not been previously reported. 0953-4075/95/040839+18$19.50 c 1995 IOP Publishing Ltd 839 840
The Journal of Chemical Physics, 2004
Rotationally cold absorption and two-photon ionization spectra of CO in the 90–100 nm region have been recorded at a resolution of 0.3–1.0 cm−1. The analyses of up to four isotopomers seek to clarify the observations in regions where the Rydberg levels built on the ground state X 2Σ+ of the ion interact with valence states of 1Σ+ and 1Π symmetry. Previous observations of the 3sσ, B 1Σ+ Rydberg state, reviewed by Tchang-Brillet et al. [J. Chem. Phys. 96, 6735 (1992)], have been extended to energies above its avoided crossing with the repulsive part of the D′ 1Σ+ valence state where resonances of varying intensities and widths have been attributed to the fully coupled 3sσ or 4sσ and D′ potentials, and where the B state approaches a second avoided crossing with the C′ 1Σ+ valence state [Cooper and Kirby, J. Chem. Phys. 87, 424 (1987); 90, 4895 (1989); Chem. Phys. Lett. 152, 393 (1988)]. Fragments of a progression of weak and mostly diffuse bands, observed for all four isotopomers, have...
Vibronic Couplings in the C 1s → n sσ g Rydberg Excited States of CO 2
The Journal of Physical Chemistry, 1996
Fragment ion yields in the C 1s f Rydberg excitation region of CO 2 were measured in the 90°and 0°d irections relative to the electric vector of the linearly polarized light. The C 1s f ns (n) 3, 4), npπ and npσ (n) 3-7), and nd (n) 3, 4) Rydberg transitions are clearly observed and show some vibrational structures. The dipole-forbidden C 1s(σ g) f 3sσ g Rydberg transition is the strongest of all the Rydberg transitions, and the ion yield in the 90°direction is dominant. This indicates that the bending vibration is predominantly coupled with the 3sσ g Rydberg state and the intensity-lending dipole-allowed state is a very strong π* resonance, only 2 eV lower than the 3sσ g state. On the other hand, in the 4sσ g Rydberg state the vibronic coupling through the antisymmetric stretching mode is strongly observed in the 0°direction. This is probably because the 4sσ g state approaches another intensity-lending state with Σ u + symmetry and goes away from the π* resonance. The angle-resolved ion-yield technique is very powerful for elucidating the vibronic coupling mechanism.
Journal of Physics B, 2011
Oxygen Is excitation and ionization processes in the CO2 molecule have been studied with dispersed and non-dispersed fluorescence spectroscopy as well as with the vacuum ultraviolet (VUV) photon-photoion coincidence technique. The intensity of the neutral O emission line at 845 nm shows particular sensitivity to core-to-Rydberg excitations and core-valence double excitations, while shape resonances are suppressed. In contrast, the partial fluorescence yield in the wavelength window 300-650 nm and the excitation functions of selected 0 + and C + emission lines in the wavelength range 400-500 nm display all of the absorption features. The relative intensity of ionic emission in the visible range increases towards higher photon energies, which is attributed to O Is shake-off photoionization. VUV photon-photoion coincidence spectra reveal major contributions from the C + and 0 + ions and a minor contribution from C 2+. No conclusive changes in the intensity ratios among the different ions are observed above the O Is threshold. The line shape of the VUV-0 + coincidence peak in the mass spectrum carries some information on the initial core excitation.
The Journal of Physical Chemistry A, 2001
The components of the 5s + 4d Rydberg complex of C 2 H 2 and C 2 D 2 have been studied by (3 + 1) photon ionization spectroscopy and fragment fluorescence excitation spectroscopy following synchrotron radiation VUV excitation. Thanks to the remarquable spectral resolution of the new synchrotron beam line SU5 at Super-ACO (12 mÅ in the range 248-65 nm), rotationally resolved spectra of Rydberg states of acetylene could be observed through their photofragment visible fluorescence. Unlike the lower 4s + 3d Rydberg complex, all Rydberg components of this complex exhibit rotational line widths typical of a 1-10 ps predissociation. The 1 Φ u 4dδ g and 1 ∆ u 4dπ g components have been characterized for both isotopic species. The relative electronic band intensities of the REMPI spectra have been interpreted within a semi-united atom model and by taking into account predissociation.
Predissociation of the 4pπL1Π Rydberg state of carbon monoxide
Chemical Physics, 2002
Time-domain and frequency-domain spectroscopic experiments have been performed on the ð4ppÞL 1 P, v ¼ 0 Rydberg state in three isotopomers of carbon monoxide. Accurate values for the excited state lifetimes of the f-parity components have been determined: sð 12 C 16 OÞ ¼ 1:08 AE 0:05 ns, sð 13 C 16 OÞ ¼ 72 AE 10 ps and sð 13 C 18 OÞ ¼ 29 AE 6 ps. The spectral resolution in the frequency-domain experiment goes as far as the limit imposed by the natural lifetime; Qbranch lines, or f-parity components of the heavier isotopes, are resolved for the first time. Highly accurate transition frequencies are determined in a molecular beam experiment using comparison and interpolation with a saturated iodine reference standard. The results reveal a number of perturbations and predissociation mechanisms, displaying a high degree of complexity in the energetic region of the 4p Rydberg states of CO with strong isotopic effects.
Journal of Electron Spectroscopy and Related Phenomena, 2007
The imaging technique has been applied to the negative fragment ion observation in the vicinity of the C1s and O1s ionization thresholds of CO 2. The O − yield curves obtained exhibit, as well as the * and Rydberg states bellow the ionization thresholds, doubly excited states above the thresholds. Anisotropic O − emissions with respect to the electric vector are seen on the images observed at the core-excited states, reflecting the symmetries of the states.
Formation of long-lived CO^{2+} via photoionization of CO^{+}
Physical Review A, 2002
The formation of long-lived CO 2ϩ from CO ϩ via photoionization in the energy range 25 to 45 eV was studied experimentally at high spectral resolution. All five allowed components of a Rydberg series with an electronically excited 3 ⌺ ϩ (ϭ0) core are identified. Four components of a second Rydberg series with a vibrationally excited 3 ⌺ ϩ (ϭ1) core and structure due to the initial vibrational state of the ion beam are also discernible. The total photoionization cross section was measured with a vibrationally relaxed CO ϩ ion beam. Franck-Condon factors from ground state CO ϩ to the relevant CO 2ϩ states were calculated.
The Journal of Chemical Physics, 1975
Dissociative excitation of CO 2 by electron impact has been studied using the methods of translational spectrosocpy and an angular distribution analysis. Earlier time-of-flight studies revealed two overlapping spectra, the slower of which has been attributed to metastable CO(a 3) fragments. The fast peak is the focus of the present study. Threshold energy, angular distribution and improved time-of-flight measurements indicate that the fast peak actually consists of five overlapping features. The slowest of the five features (1) is found to consist of metastable 0(5S) produced by predissociation of a Zu + / i state of CO into 0(5S) + CO(a 3T~ Oxygen Rydberg fragments originating 2 + directly from a different E state are believed to make up the next fastest feature (2). Mechanisms for producing the three remaining features are discussed.