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
Filter
Datenquelle
Materialart
Erscheinungszeitraum
  • 1
    Digitale Medien
    Digitale Medien
    Rotationally inelastic collisions of a molecule in a 1Δ electronic state: NH(a 1Δ) (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 5316-5323 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The general theory for inelastic scattering of molecules 1Δ electronic states is outlined and applied to the specific case of 1Δ states arising from a π2 electron occupancy, e.g., NH(a 1Δ). Integral cross sections for rotational transitions out of the lowest rotational level (J=2) of NH(a 1Δ) v=0 are reported for several targets. A pulsed beam of rotationally cold NH(a 1Δ) was produced by 193 nm photolysis of a dilute mixture of hydrazoic acid in nitrogen seed gas at the tip of a nozzle. The target beam was also prepared as a pulsed supersonic beam. The final rotational state distribution was measured in the collision zone by laser fluorescence excitation. The state-to-state cross sections were found to decrease significantly with increasing final rotational quantum number J'. The magnitude of the J=2→J'=3 cross sections were compared for the different targets. Isotopic scrambling in NH(a 1Δ)–D2 collisions was also searched for but not observed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.457579
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 2
    Digitale Medien
    Digitale Medien
    The vibronic state distribution of the NCO(X˜ 2Π) product from the CN+O2 reaction (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 1696-1707 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The vibronic state distribution of the NCO product from the CN+O2 reaction has been extracted from a laser fluorescence experiment in a cell at a total pressure of 140 mTorr. The CN reagent was prepared by 193 nm photolysis of cyanogen, and individual NCO vibronic levels were interrogated by fluorescence excitation in its A˜ 2Σ+−X˜ 2Π band system after a variable delay. A finite induction time was observed for the formation of the NCO product in all detected vibronic levels, indicative of the necessity to moderate the translational and rotational energy of the CN photolysis fragment before appreciable reaction can occur. The NCO product was observed in 80 different vibronic levels, with energies up to 51.5 kJ/mol. A nascent vibronic state distribution among the various (v1,v2) Renner–Teller components was estimated from the relative intensities of the various bands. While it was not possible to determine the distribution in the v3 levels because of insufficiently accurate spectroscopic data, it is nevertheless clear that the NCO product from CN+O2 is formed with considerable vibrational excitation. These results are consistent with previous kinetic studies which suggest that the reaction occurs on an attractive potential energy surface, with no activation barrier.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.461020
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 3
    Digitale Medien
    Digitale Medien
    Determination of the internal state distribution of NO produced from the H+NO2 reaction (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 2389-2396 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The internal state distribution of the NO product from the H+NO2 reaction was determined in a crossed-beam experiment. Rotational populations in the v=0 to 2 vibrational levels of NO were derived from laser fluorescence excitation spectra of the A2Σ+–X 2Π band system. The vibrational distribution decreases monotonically with v, and the rotational state distribution is peaked at low J (most probable J of approximately 11.5), but the tail of the distribution extends out to N≈50. After correction for the flux-density transformation, the vibrational population distribution is found to equal 1:0.17±0.04:0.05±0.02 for v=0,1,2, respectively. The lower F1(Ω=1/2) spin-orbit component is preferred over the F2(Ω=3/2) manifold by a ratio of 1:0.52±0.11, independent of vibrational level. At high J, a preference for the Π(A') Λ doublet levels is observed. Approximately 9.5%±2% of the reaction exoergicity is found in NO internal excitation. The NO and previously determined OH internal state distributions are compared with statistical distributions calculated by phase-space theory. The energy disposal in OH is found to be greater than statistical, while the opposite is true for NO, as might be expected in a direct reaction of the type A+BCD→AB+CD for the "new'' and "old'' bonds, respectively. The Λ doublet preference observed here for the NO product, and previously for the OH product, can be explained by the dissociation of an HONO(X˜ 1A') intermediate. A mechanism for the generation of unequal NO spin-orbit populations, involving nonadiabatic mixing in the exit channel, is proposed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.457981
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 4
    Digitale Medien
    Digitale Medien
    Observation of highly excited bending levels in NCO(X˜ 2Π) (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 5448-5456 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: New NCO A˜ 2Σ+–X˜ 2Π vibronic bands in the (0,v2,0)–(v1,v2,v3) sequences, with (v1,v3)=(0,0), (1,0), (0,1), (1,1), and (2,0), are reported. These bands have been observed in laser fluorescence excitation experiments of NCO produced in the CN+O2 reaction, where CN was prepared by 193 nm photolysis of cyanogen. The measured bandhead wave numbers were used to derive term values for a number of NCO(X˜ 2Π) vibronic levels, which were then fit to a model Hamiltonian.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.459641
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 5
    Digitale Medien
    Digitale Medien
    Comment on: Observation of highly excited bending levels in NCO(X˜ 2 Π) (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 2222-2222 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.460976
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 6
    Digitale Medien
    Digitale Medien
    Internal state distribution of OD produced from the O(3P)+ND2 reaction (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 955-962 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The internal state distribution of the OD product from the O(3P)+ND2 reaction was determined in a crossed beam experiment. Rotational state populations in the OD v=0 vibrational level, and an upper bound to the v=1 to v=0 ratio, were derived from A 2Σ+–X 2Π laser fluorescence spectra. The OD internal state distribution was found to be very cold, with only ∼8% of the available product energy appearing as OD excitation. While this reaction is believed to proceed through D2NO and DNOD intermediates, the observed rotational state distribution is much colder than those predicted by statistical theories. The implications of these experimental results for the reaction dynamics are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.461050
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 7
    Digitale Medien
    Digitale Medien
    Radiative and nonradiative decay of the NH(ND) A 3Π electronic state: Predissociation induced by the 5Σ− state (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 1913-1922 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Lifetimes for excited ND A 3Πv'=1–3 and NH v'=2 in specified rotation/fine-structure levels were determined by excitation on isolated rotational lines in the A 3Π–X 3Σ−Δv =+1 sequence, using molecules prepared in a pulsed supersonic beam. The observed lifetimes for NH v'=2 levels were found to be significantly shorter than those expected for purely radiative decay, indicative of additional removal of excited-state population by predissociation. The observed fine-structure dependence of the removal rates is consistent with a mechanism in which the A 3Π state is predissociated by spin–orbit coupling to the repulsive 1 5Σ− state which correlates with the ground-state asymptote, N(4S)+H(2S). This mechanism is also expected to be responsible for the previously observed predissociation of high N' levels in NH v'=0 and 1. By contrast, no significant evidence for predissociation was found for the decay of excited ND v'=1–3 for the low J' levels investigated. These observations were confirmed with a combination of ab initio electronic structure, and coupled electronic state dynamics, calculations. Using an extended contracted Gaussian basis and large configuration state function expansions(160 000–380 000 terms) potential energy curves for, and spin–orbit induced coupling (using the full microscopic Breit–Pauli interaction) between, the A 3ΠΩ and 1 5Σ−Ω states were determined. These electronic structure data were used as the basis for the determination of the radiationless decay rates using a semiclassical coupled state model. These results were in turn combined with radiative decay rates for the A 3Π→X 3Σ− transition to determine the total decay rates which were found to be in excellent accord with the available experimental observations, thereby confirming the mechanism of the predissociation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.459912
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 8
    Digitale Medien
    Digitale Medien
    Cluster effects in O3/H2O photochemistry: Dynamics of the O+H2O→2OH reaction photoinitiated in the O3⋅H2O dimer (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 4200-4210 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The dynamics of the 266 nm photoinitiated reaction of 16O3 and H218O were studied using 16O3⋅H218O van der Waals dimers to orient the initial reagents. In the absence of perturbations, the geometry of the 16O3⋅H218O dimer is such that 266 nm photolysis of cluster-bound ozone initiates glancing O+H2O trajectories, with a 3 A(ring) impact parameter. Laser induced fluorescence probes show that 81±7% (2σ) of the "new''-16OH and essentially all of the "old''-18OH products were formed with v=0, with a slight preference for the Π(A') Λ doublets, and average rotational energies of 900±130 and 760±80 cm−1, respectively. Approximately 19% of the "new''-16OH products form with v=1 and average rotational energy of 930±210 cm−1. No significant OH scattering anisotropy or other vector correlations were observed. Sub-Doppler resolution experiments showed average kinetic energies for new-16OH(v=0) products about 19% higher than for old-18OH(v=0) products in the same rotational levels; increasing from values of about 500 cm−1 at low rotational levels, to about 1500 cm−1 at the highest rotational levels populated. Similar OH internal and kinetic energies were observed when the clusters were photolyzed at 281.5 nm. These dimer results are very different from those observed for the bimolecular O(1D)+H2O→2OH reaction, photoinitiated in gas phase mixtures of 16O3 and H218O. The gas phase O(1D)+H2O→2 OH reaction produces OH with pronounced recoil anisotropy, these OH products carry far more internal energy than seen in the cluster products, and there is greater disparity between the internal energies of the gas phase 16OH and 18OH products. Evidently, cooperative effects in the cluster environment result in a significant change in reaction path.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.466304
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 9
    Digitale Medien
    Digitale Medien
    Product kinetic energies, correlations, and scattering anisotropy in the bimolecular reaction O(1D)+H2O→2OH (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 5919-5922 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Doppler spectroscopy of the 16OH and 18OH products of the 16O(1D)+H218O reaction reveals marked c.m. reactive scattering anisotropy: 16OH scatters in the hemisphere containing the 16O-atom velocity vector. Internal energies of geminate OH fragments are correlated: fragments of high internal energy form with cofragments of low internal energy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.463753
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    Artikel (Nationallizenzen)
    Volltext
  • 10
    Digitale Medien
    Digitale Medien
    Nascent product states in the photoinitiated reaction of O3 and H2O (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 952-961 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: The rotational, vibrational and fine-structure state distributions for the reaction 16O(1D)+ H218O →16OH +18OH, triggered by 266 nm photolysis of O3, have been measured under conditions where less than 1% of the nascent fragments experienced collisions prior to detection. The distributions are qualitatively different than those reported earlier for 266 nm photolysis, which were evidently affected by collisions. The rotational and vibrational state distributions are similar to recent 248 nm photolysis experiments, but with differences attributed to collisional and/or energetic effects in those experiments. The "new'' 16OH is formed with vibrational populations in the ratio 0.39(v=0):0.29(v=1):0.3(v≥2). Gaussian rotational energy distributions peaked near N=12 give average rotational energies of 〈Erot〉 = 3440 and 2780 cm−1 for 16OH v=0 and v=1, respectively. The "old'' 18OH is much colder with vibrational populations 0.94(v=0):0.06(v=1) and a 18OH v=0 Gaussian rotational energy distribution characterized by 〈Erot〉 = 1920 cm−1.There is negligible rotational alignment of the 16OH fragments [βμJ' = β20(02) = 5A(0)2/4 = 0.06± 0.09], which is significantly less than expected for fragment rotations aligned with respect to the O+H2O relative velocity vector. The spin-orbit propensities deviate slightly from the statistical expectation and are characterized by [F2,N]/[F1,N]=(0.89±0.06) ×N/(N + 1). The Λ-doublet distributions for 18OH (all N) and 16OH (low-to-moderate N) fragments conform to an unconstrained-dynamics prior distribution. A slight propensity for Π(A') in excess of this expectation is seen for the 16OH (high N) fragments. These new results are discussed in terms of possible insertion and abstraction mechanisms for the reaction.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.463198
    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...