Bibliothek

X
feed icon rss

Ihre E-Mail wurde erfolgreich gesendet. Bitte prüfen Sie Ihren Maileingang.

Leider ist ein Fehler beim E-Mail-Versand aufgetreten. Bitte versuchen Sie es erneut.

Vorgang fortführen?

Exportieren
  • 1
    Digitale Medien
    Digitale Medien
    Resonant multiphoton ionization dynamics of N2 via the a 1Πg(v=10–14) states: Preparation of state-selected N+2 X 2Σ+g(v+=0–4) ions (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 7823-7827 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The photoelectron spectra are reported from resonantly enhanced multiphoton ionization of N2 via the a 1Πg(v=10–14) states. Ionization from these levels is found to follow a (2+1) pathway resulting in N+2 X 2Σ+g(v+=0–4) ions. The observed branching ratios in the photoelectron spectra reveal a strong propensity for forming ground state ions in a single vibrational state. The results are explained qualitatively by favorable Franck–Condon overlap in the ionizing X 2Σ+g–a 1Πg transition.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.461311
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 2
    Digitale Medien
    Digitale Medien
    Photoelectron angular distributions and vibrational branching ratios of CO (2+1)-photon ionization via the B 1Σ+ state (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 4334-4339 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We present vibrational branching ratios and photoelectron angular distributions for resonantly enhanced (2+1)-photon ionization of CO. The excitation ladder involves the B 1Σ+(vi=0 or 1) Rydberg state. Contrary to expectations fostered by the Franck–Condon principle, ionization via vi=0 branches into vibrational states v+=0–4. Such phenomena are also observed in the case of vi=1, but only to a minor extent. The angular emission patterns of the photoelectrons ejected during the ionizing step are of distinct character in that they are highly anisotropic for Δv=vi−v+=0 processes, but show isotropy when due to Δv≠0 transitions. The photoelectron angular distribution which accompanies the Δv=0 ionization of B(vi=1) shows p-wave character, and hence we may postulate a spherical potential of the Rydberg ion core. The same approximation should hold for the vi=0 state. The dissimilar appearance of the angular distributions when ionizing from this level invites the hypothesis of two individually different ionization channels.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.466087
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 3
    Digitale Medien
    Digitale Medien
    Photoelectron angular distribution and ion vibrational branching ratio: The (2+1)-photon ionization of E 1Π-state-aligned CO molecules (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 7687-7695 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We report vibrational level channeling and photoelectron angular distributions which characterize the single-step photoionization of the E 1Π Rydberg state of CO. Particular attention is paid to the influence of the intermediate state's rotational preparation and its spatial alignment. The two-photon excitation is tuned to populate the lowest possible J values of E, which permits us to isolate a single magnetic sublevel of this intermediate state. Vibrational branching is found to be insensitive to the choice of the excitation line and does not match the predictions suggested by the Franck–Condon factors for a CO E 1Π(v1)→CO+ X 2Σ+(v+) direct ionization. A competitive autoionization from the three-photon-energy state S1 may be responsible for this anomalous behavior. The phenomenological pattern of photoelectron distributions can in all cases be rationalized on the basis of the intermediate state alignment. A separate chapter of the discussion is devoted to P(2) pumping, since it provides a particularly simple situation where all excited molecules are oriented with their axes parallel to the light vector E, which makes this case tractable to a quantitative calculation. Its results show qualitative agreement with the experimental observations. The remaining discrepancy can be attributed to the autoionization which has not been considered in the calculation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.465698
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 4
    Digitale Medien
    Digitale Medien
    A high-intensity multi-purpose piezoelectric pulsed molecular beam source (1989)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 713-716 
    Details
    ISSN: 1089-7623
    Quelle: AIP Digital Archive
    Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: A piezoelectric valve is described which delivers intense gas pulses limited by the nozzle for diameters of up to 1.0 mm. Minimum pulse lengths between 0.15 and 0.25 ms (fwhm) are obtained at full opening, depending on the nozzle size. The upper limit of the repetition rate is near 1 kHz. The valve and its modifications meet almost all experimental requirements. In particular, ways of operating in a wide temperature range are outlined. Reliable operation with a remote nozzle at 77 K was recently demonstrated. Nozzle temperatures of more than 1000 K should be possible with a similar setup.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1141006
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 5
    Digitale Medien
    Digitale Medien
    A guided-ion beam study of the hydrogen atom transfer reaction of state-selected N+2 with H2 at collision energies ranging from subthermal to 2 eV (c.m.) (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 214-225 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: This article presents detailed internal and kinetic energy dependent cross sections and reaction rates for the hydrogen atom transfer processes N+2(X 2Σ+g, v+=0–4, J+=2)+H2→N2H++H, which were obtained under single-collision conditions in a guided-ion beam/scattering gas experiment. Preparation of ions in specific states relied on single-color excitation within a resonantly enhanced (2+1) multiphoton ionization scheme. The translational energy of the ions, Elab, was varied from 0.1 eV to approximately 30 eV. A small activation barrier impedes the reaction. Vibronic state preparation of the nitrogen ion is influential on the nature of the energy surface—N+2+H2 or H+2+N2—along which the H atom transfer proceeds. Calculations of model potential energy surfaces suggest that the reaction pathway must involve several exoergic and endoergic channels which open successively as the collision energy increases. A purely collision determined cross section—as would be evidenced by the E−1/2 dependence formulated in the Langevin–Gioumousis–Stevenson model—is observed only within a narrow window of kinetic energies. © 1995 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.469394
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 6
    Digitale Medien
    Digitale Medien
    Rovibronic energy transfer from N2(a 1πg) to CO(A 1π) studied by laser REMPI spectroscopy (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 2742-2749 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The collision-induced electronic energy transfer N2(a 1πg,v′) +CO(X 1Σ+,v″=0) →N2(X 1Σ+g,v″) +CO(A 1πg,v′)+ΔE is studied in a gas cell. N2(a 1πg,v′, J′) is prepared by two-photon (2hν1) absorption from the ground state. CO(A 1πg,v′, J′) is probed by two-photon (hν1+hν2) ionization via CO(B 1Σ+) as the resonant intermediate state. Experiments show that the overall energy transfer cross sections exceed that of gas kinetic collisions by a factor of 3–4. The energy mismatch ΔE is the determining factor controlling the branching ratio from one N2(1πg,v′) donor to different vibrational levels of CO(A 1π,v′). For small values of ΔE, CO(A 1πg,v′, J′) shows a Boltzmann-like rotational level population. Its rotational temperature scales with ΔE. About 28% of the excess energy funnels into the rotation of CO(A 1π). An explanation for the observed rotational distribution of CO* and the energy transfer mechanism is given. The rate constants are analyzed in terms of the surprisal.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.453061
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 7
    Digitale Medien
    Digitale Medien
    The hydrogen atom abstraction reaction CO++H2→HCO++H: Translational and internal energy dependence of the integral cross section (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 527-533 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The widely accepted model descriptions of ion–molecule reactions suggest identical rate constants for the title reaction and the analogous, isoelectronic system N2++H2, which has been the topic of a previous publication from this laboratory. A comparison of both data sets, however, reveals substantial disagreement which we attribute to the absence of energetic resonances between the reagents which characterized the N2+/H2 system. Resonantly enhanced photoionization was exploited to accomplish the state-specific preparation of CO+ (X 2Σ+, v+=0,1). A monoenergetic beam of vibrationally selected ions, tuned within the range 0.01 eV≤Ecm≤10 eV, transits a scattering chamber which confines the neutral, H2. The title reaction was the only channel observed—no evidence of charge transfer or dissociative ionization could be detected. The hydrogen atom transfer turns out to proceed directly. The reactive cross section fails to show the E−1/2 dependence indicative of collision determined processes. The experimental data are perfectly mimicked by an expanded Langevin model which includes additional attractive potential terms. In contrast to the N2+/H2 case, vibrational excitation does not affect the rate of the reaction. © 1998 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.475416
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 8
    Digitale Medien
    Digitale Medien
    State-selected ion-molecule reactions: The charge-transfer N2+(X,v+)+O2→O2++N2 (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 9426-9434 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The charge-transfer process, which is the subject of this paper, is an important link in the chain of reactive events which occur in the E- and F-regions of the earth's atmosphere. The reaction is suspected to proceed via the formation of a short-lived intermediate complex (N2⋅O2)+. The transient existence of this van der Waals molecule has been inferred from molecular orbital and ab initio arguments. To the present day, however, none of the numerous studies focusing on this system has provided proof of its existence. The positive evidence obtained from this experiment is of an indirect nature, based on measurements of the kinetic energy of the released O2+ as a function of the expendable center-of-mass collision energy. The results point to an indirect reaction (i.e., via an intermediate) in the low energy regime, and a direct process once the center-of-mass energy exceeds the bond energy of the complex. A model description which contracts both pictures matches the complete set of energy-dependent cross section data in a very persuasive manner. A competing reactive channel which has also been given attention results in the formation of NO+. The initiation of this reaction requires a cleavage of the N–N bond, which should be eased by vibrational excitation of the reagent ion. The cross section data, however, turn out to be unaffected by such details of reagent state preparation. © 1999 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.478907
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 9
    Digitale Medien
    Digitale Medien
    Rotational transitions of N2(a 1Πg) induced by collisions with Ar/He and N2(a 1Πg)–N2(X 1Σ+g) rovibronic energy transfer studied by laser REMPI spectroscopy (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 5251-5255 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: This paper reports the results of two related experiments: (A) The state-to-state rotational transition probabilities of N2(a 1Πg) in collisions with rare gas atoms (Ar or He) were measured by the technique of two-step multiphoton ionization. Results show that the selection rule antisymmetric–symmetric is obeyed. The transition probability drops rapidly with increasing ||ΔJ||. A propensity rule related to the Π+ or Π− symmetry conservation of the electronic wave function during the collision induced rotational transition holds. (B) The cross section for the rovibronic energy transfer between N2(1Πg) and N2(X 1Σ+g) is found to be ∼28 A(ring)2. N2(a 1Πg) product populations show a Boltzmann-like distribution with a rotational temperature suggesting an equipartition of the available energy among the rotational and translational degrees of freedom of the products. A mechanism invoking an intermediate collision complex along with intermolecular electron exchange may explain the results.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.453667
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 10
    Digitale Medien
    Digitale Medien
    Resonance-Enhanced 2 + 2 Photon Ionization of Nitrogen: The Lyman-Birge-Hopfield Band System
    Amsterdam : Elsevier
    Journal of Molecular Spectroscopy 162 (1993), S. 184-229 
    Details
    ISSN: 0022-2852
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1006/jmsp.1993.1279
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
Schließen ⊗
Diese Webseite nutzt Cookies und das Analyse-Tool Matomo. Weitere Informationen finden Sie hier...