Library

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 6508-6518 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: State-resolved cross sections for the inelastic scattering of OH(X 2Π) with CO and N2 have been measured in a crossed molecular beam apparatus over the energy range from 0.5 to 5.5 kcal mol−1. The magnitude and shape of the excitation functions for the same OH final states were virtually independent of the two targets except near threshold. Both spin–orbit conserving and spin–orbit changing transitions have been investigated. Cross sections for spin–orbit changing transitions of large ΔN were approximately the same magnitude as those for spin–orbit conserving transitions. For small ΔN, however, the spin–orbit conserving transitions became more favorable. The Λ-doublet ratio, Π(A')/Π(A‘), in the Π3/2 (F1) manifold differed from unity only for the N2 target for which the ratio became increasingly larger than unity as N' increased. The observed fine-structure effects were nearly the same as those from the corresponding (reverse) reactive collisions, and a close connection between the inelastic and reactive events has been conjectured.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 1478-1479 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reaction CN+O2→NCO+O has been investigated in a crossed-molecular beam experiment at a collision energy of 0.76 kcal/mole. Internal state distributions of the ground state NCO(X˜ 2Π3/2, 0010,J,e/f) products have been measured by laser-induced fluorescence. The rotational excitation is small. There is an observed preference in the population of the K doublet fine-structure states, 1f〉1e, and this preference is even stronger for low J states.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 2443-2459 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The state-to-state integral cross sections for the isotopic exchange reaction of CH(X 2Π) with D2 to produce CD(X 2Π) have been measured in a crossed-beam apparatus by the laser-induced fluorescence method. Two types of measurements were performed: (1) the translational energy dependence of an individual quantum state of the product and (2) the state distribution of the products at fixed and well-defined translational energy. To understand some of the finer details of the reaction dynamics similar experiments were also carried out on the reaction CD(X 2Π) with H2 to give CH(X 2Π). For the isotopic exchange channel, the cross section decreased rapidly with increasing translational energy, signifying a complex formation reaction mechanism. The CD(CH) product rotational level distributions are substantially colder than a statistical expectation and are interpreted as the result of a multiple-impact collision between the receding products in the exit channel. A novel frequency-locking mechanism, similar to that proposed to understand the dynamics of inelastic collisions between CH and D2 (the preceding paper), is suggested to explain anomalous peaks in the product rotational level distribution for the isotopic exchange channel. However, the fine-structure state distributions for the reactive process, which are very different from that for the inelastic channel, cannot be rationalized by conventional interpretation. Some basic concepts about fine-structure selectivity in chemical reactions have been developed. With these concepts, it is conjectured that the fine-structure state distributions of open-shell molecules arising from reactive encounters could provide a "fingerprint'' of the electronic wave function at the transition state.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 821-838 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The state-to-state integral cross sections for the inelastic scattering of CH(X 2Π) with He were measured in a newly constructed crossed molecular beam machine. Use of laser-induced fluorescence in an unconventional flux mode of detection provided single fine-structure state specific detection of the products. Two types of measurements were performed to further our understanding of the collision dynamics of open shell systems: (1) the product state distribution at a fixed and well-defined collision energy and (2) the dependence on collision energy of product state-resolved cross sections. A qualitative understanding of the collision dynamics can be obtained by properly factoring out features dependent on the fine-structure states, i.e., effects involving individual Λ-doublet states and features dependent on the rotational level alone, i.e., effects remaining after summing over all four fine-structure states associated with a given rotational quantum number. As for the fine-structure effects, a preferential population of product Λ-doublet states with reflection symmetry Π(A‘) was observed. The physical origin of this observed electronic orbital alignment can be attributed to a quantum interference phenomenon, as detailed in the accompanying paper. At the rotational level, the dominance of rotational rainbow scattering is unambiguously identified from both the existence of dynamical thresholds and a strong correlation between rotational level distributions at fixed translational energy and level specific excitation functions. These effects combined with other experimental observations lead us to visualize the CH+He scattering dynamics in a novel fashion. The collision can be regarded as a series of approximately independent sequential events each mediated by different regions of the interaction potential during the course of the whole encounter.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 4443-4444 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The title reaction was studied in a new crossed molecular beam apparatus. Laser-induced-fluorescence was used to characterize both the reactant CH radical and the product CD radical in a state-resolved manner. Two types of dynamical information are reported here: (1) the excitation function for a specific reaction product state and (2) the product rotational state distribution at a well-defined collision energy.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 2431-2442 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The state-to-state integral cross sections for the inelastic scattering of CH(X 2Π) and D2 to produce rotationally excited CH(X 2Π) product have been measured in a crossed-beam apparatus by the laser-induced fluorescence method. Two types of measurements were performed: (1) the translational energy dependence of an individual quantum state of the product and (2) the state distribution of the products at fixed and well-defined translational energy. For the inelastic scattering channel, the cross sections gradually increased from a dynamical threshold to a broad maximum and then slowly decreased as the translational energy increases. Evidence for multiple-impact rotational rainbows was found and a possible frequency-locking phenomenon between the two receding rotors resulted. Moderate orbital alignment was observed except for the highest rotational levels of the product. By comparing and contrasting the kinematically similar system CH(X 2Π)+He, the influence of a strongly attractive potential energy surface on the inelastic scattering of CH+D2 was inferred. Combining the results of the inelastic scattering and the isotopic exchange channels (the following paper) provide an unprecedented look into the dynamics of collisions between CH(X 2Π) and D2.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 6689-6699 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The dynamics of the reactions of translationally energetic H atoms with BrCN, ClCN, and (CN)2 was studied by determining both the rotational state distribution and the translational energy disposition of the CN product ground vibrational level. The reaction was carried out using H atoms with a most probable translational energy of 92 kJ mol−1. The CN radical was monitored by time- and frequency-resolved absorption spectroscopy using the CN red system (A 2Π←X 2Σ) (2,0) band near 790 nm. Sub-Doppler resolution spectroscopy was used to determine the initial translational temperature of the CN(0,J) product. The fraction of the available reaction exothermicity that appeared as CN(0) rotational energy, fR, for H+XCN→HX+CN was 0.034±0.006, 0.061±0.02, and 0.13±0.007, for X=Br, Cl, and CN, respectively. Likewise, the fraction of the available reaction exothermicity that appeared as relative product translational energy, fT, was 0.52±0.25, 0.52±0.20, and 0.59±0.05, for X=Br, Cl, and CN, respectively. The absolute reaction cross sections for the H+XCN→HX+CN reactions were also measured to be 0.03, 0.02, and 0.3×10−16 cm2 for X=Br, Cl, and CN, respectively. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The integrated-absorption coefficients of several hyperfine lines of the magnetic dipole allowed transition of the bromine atom, Br, center at 3685.2 cm−1 were measured, and a value for the square of the magnetic dipole transition moment of the Br atom was determined. A theoretical calculation for the magnetic dipole transition moment was also carried out using a relativistic ab initio atomic structure formulation. The theoretical value was in excellent agreement with the value predicted assuming pure LS coupling, and in reasonable agreement with experiment. The Br atom was generated in equal concentration with the cyano radical (CN) by the 193 nm photolysis of cyanogen bromine, BrCN. The CN radicals were titrated by the rapid reaction with C3H8 to generate HCN and a small amount of HNC. Both time-resolved and frequency-scanned infrared absorption spectroscopy were used to monitor the Br, HCN, and HNC species. The photolysis of BrCN at 193 nm produced both the ground state Br(2P3/2) and the spin-orbit excited Br(2P1/2) atoms, and the yield for the production of Br(2P1/2) atoms was measured to be 0.31±0.01. The rate constants for the quenching of Br(2P1/2) by BrCN and C3H8 at 293 K were also determined. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 4224-4236 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The reaction of the cyano radical (CN) with hydrogen was studied by time-resolved infrared absorption spectroscopy of individual rovibrational states of HCN. The initial vibrational level distribution of HCN(v10v3) was determined by plotting the time dependence of the fractional population of a vibrational level and extrapolating these curves to the origin of time. The experiments were carried out at two temperatures, 293 and 324 K, with similar results. It was estimated that about 50% of the available reaction exothermicity was deposited as vibrational excitation of the HCN product. Surprisingly, the HCN(101) vibrational level received a significant fraction of the observed vibrational population, implying that the CN vibration was not really a spectator bond in the reaction dynamics. Furthermore, the observed HCN(v10v3) vibrations only account for about 27% of the initial HCN population produced in the title reaction. A significant fraction of the product HCN molecules must have been produced with the bending mode excited, likely in combination with the H–C stretch vibrations. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 109 (1998), S. 6312-6319 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The square of the electronic–vibrational transition moment for the (2,0) band of the cyano radical (CN), A 2Π←X 2Σ+, red system at 789.5 nm has been determined using a direct time-resolved absorption technique. The line strength of the R1(8.5) transition of 12C14N was measured by comparison to the known line strength of the H12C14N(001)←(000) P(8) infrared υ3 fundamental transition near 3.05 μm. The CN radical was created by pulsed-laser photolysis of cyanogen, (CN)2, in a mixture of H2 and (CN)2 in either Ar or He carrier gas at 293 K. Both CN and HCN were monitored by time-resolved absorption spectroscopy during the same photolysis laser pulse. A simple kinetic model was used to relate the two absorption features to each other. The square of the electronic–vibrational transition moment for the A←X(2,0) band was found to be 7.8±1.0×10−38 esu2 cm2 in good agreement with theoretical calculations based on ab initio quantum chemistry methods. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...