Library

X
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
    The dipole moment function and vibrational transition intensities of OH (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 5455-5465 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The relative intensities of nine pairs of rovibrational transitions of OH in the v=1←0 fundamental have been measured by flash kinetic infrared absorption spectroscopy. Each pair of transitions originates from a common rotational and spin–orbit state, so that relative intensities are independent of the OH number density and quantum state distribution. The relative intensities are strongly J dependent and this dependence provides detailed information about the shape of the OH dipole moment function, μ(r), and hence the absolute infrared transition strengths. In an accompanying paper we present the theoretical basis for extracting μ(r), for an open shell diatomic like OH, from relative infrared intensities and permanent dipole moment measurements (Peterson et al.). In this work we implement those ideas and determine the OH dipole moment function to be: μ(r)=1.6498(6) D+0.561(32) D/A(ring) (r−re )−0.75(17) D/A(ring)2 (r−re )−1.5(11) D/A(ring)3(r−re )3. The accuracy of μ(r) is excellent near re (re =0.970 A(ring)), since the data used to derive it are from low vibrational states. The useful range of this function extends from approximately 0.75 to 1.35 A(ring). The rotationless Einstein A coefficient for the OH fundamental is determined from μ(r) to be 16.7(19) Hz. This is in considerable disagreement with most other experimental and theoretical results, but is in good agreement with theoretical calculations by Mies (18.3 Hz) and by Langhoff et al. (13.8 Hz).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456451
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Absolute infrared transition moments for open shell diatomics from J dependence of transition intensities: Application to OH (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 5443-5454 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A general approach to the determination of the dipole moment function and of the absolute vibrational transition moments for diatomic molecules is presented. This method utilizes the variation of intensity with J within a vibrational transition, together with permanent dipole moment information, to extract the absolute transition moments. An essential feature of the model is its use of algebraic expressions for calculating vibration–rotation line intensities. These expressions can be rapidly evaluated in a least squares fit which determines the dipole moment function. This approach is general in that it is not limited to 1Σ state molecules, nor to the simplest of Hund's case couplings of spin, orbital and mechanical angular momentum. It is also not limited to molecules with essentially linear dipole moment functions. The model is successfully applied to the OH molecule which violates each of these restrictions. In the accompanying work we report experimental measurements of relative infrared absorption intensity measurements for OH v=1←0 transitions and the extraction of an experimental μ(r) using the approach presented here.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456450
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    H+O3 Fourier-transform infrared emission and laser absorption studies of OH (X 2Π) radical: An experimental dipole moment function and state-to-state Einstein A coefficients (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 7003-7019 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The relative intensities of 88 pairs of rovibrational transitions of OH (X 2Π) distributed over 16 vibrational bands (v'≤9, Δv=−1,−2) have been measured using Fourier transform infrared (FTIR) emission/absorption spectroscopy. Each pair of transitions originates from a common vibrational, rotational, and spin–orbit state, so that the measured relative intensities are independent of the OH number density and quantum state distribution. These data are combined with previous v=1←0 relative intensity absorption measurements and v=0, 1, and 2 permanent dipole moments to determine the OH dipole moment function as a cubic polynomial expanded about re, the equilibrium bond length. The relative intensities provide detailed information about the shape of the OH dipole moment function μ(r) and hence the absolute Einstein A coefficients.The intensity information is inverted through a procedure which takes full account of the strong rotation–vibration interaction and spin uncoupling effects in OH to obtain the dipole moment function (with 95% confidence limits): μ(r)=1.6502(2) D+0.538(29) D/A(ring) (r−re)−0.796(51) D/A(ring)2 (r−re)2−0.739(50) D/A(ring)3 (r−re), 3 with a range of quantitative validity up to the classical turning points of the v=9 vibrational level (i.e., from 0.70 to 1.76 A(ring)). The μ(r) determined in this study differs significantly from previous empirical analyses which neglect the strong effects of rotation–vibration interaction and spin uncoupling. The present work also permits distinguishing between the various ab initio efforts. Best agreement is with the dipole moment function of Langhoff, Werner, and Rosmus [J. Mol. Spectrosc. 118, 507 (1986)], but their theoretical predictions for higher overtone transitions are still outside of the 2σ experimental error bars. Absolute Einstein A coefficients from the present μ(r) are therefore presented for P, Q, R branch transitions for Δv=1, 2, 3, v'≤9, J'≤14.5, in order to provide the most reliable experimental numbers for modeling of near IR atmosphere OH emission phenomena.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459476
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    High-resolution infrared flash kinetic spectroscopy of hydroxyl radicals (1991)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 95 (1991), S. 2629-2636 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100160a004
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Rotationally inelastic scattering in CH4+He, Ne, and Ar: State-to-state cross sections via direct infrared laser absorption in crossed supersonic jets (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 3497-3516 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Absolute integral state-to-state cross sections are reported for rotationally inelastic scattering in crossed jets of CH4 with the rare gases He, Ne, Ar, at center of mass collision energies of 460±90, 350±70, and 300±60 cm−1, respectively. CH4 seeded in Ar buffer gas is cooled in a pulsed supersonic expansion into the three lowest rotational levels allowed by nuclear spin statistics corresponding to A(J=0), F(J=1), and E(J=2) symmetry. Rotational excitation occurs in single collisions with rare gas atoms from a second pulsed supersonic jet. The column integrated densities of CH4 in both initial and final scattering states are subsequently probed in the jet intersection region via direct absorption of light from a narrow bandwidth (0.0001 cm−1), single mode color center laser. Total inelastic cross sections for collisional loss out of the J=0, 1, and 2 methane states are determined in absolute units from the linear decrease of infrared absorption signals as a function of collider gas concentration. Tuning of the ir laser source also permits probing of the collisionally excited rotational states with quantum state and velocity resolution; column integrated scattering densities are measured for all energetically accessible final states and used to infer absolute inelastic cross sections for state-to-state energy transfer. The observed trends are in good qualitative agreement with quantum state resolved pressure broadening studies; however, the dependences of the rotationally inelastic cross sections on nuclear spin modification (i.e., J) and rotational inelasticity (i.e., ΔJ) is not well predicted by conventional angular momentum or energy gap models. More rigorous comparison with the quantum state-resolved scattering data is obtained from full close coupled scattering calculations on trial potential energy surfaces by Buck and co-workers [Chem. Phys. Lett. 98, 199 (1983); Mol. Phys. 55, 1233, 1255 (1985)] for each of the three CH4+rare gas systems. Agreement between theory and experiment for He+CH4 is nearly quantitative, but some discrepancies are noted for the heavier rare gases. Finally, the possible influence of sequential collision channels on the measurement of the smallest observable cross sections is investigated via a master equation analysis. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472211
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    A new direct infrared laser absorption method for state-to-state rotational energy transfer in crossed supersonic jets: Experimental results and quantum scattering analysis for Ar+CH4 (1993)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 9513-9521 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new method for measuring state-to-state rotational energy transfer in crossed supersonic beams is described. The method is based on direct absorption of tunable, high-resolution infrared laser light by target molecules collisionally excited into final rotational states. The direct IR absorption approach offers high sensitivity, full quantum state resolution, a Doppler probe of final velocity components, and is applicable to any target molecule that absorbs in the near IR. Preliminary results are presented for Ar+CH4 scattering in crossed supersonic beams at a mean center-of-mass collision energy of 41 meV. Because of the high spectral resolution, the method can readily distinguish rotational fine structure states of A, F, and E symmetry in the tetrahedral group, as well as the much more energetically separated final j states. The results are compared with full quantum close-coupling calculations on two different Ar+CH4 potential energy surfaces. The state-to-state scattering results provide a sensitive measure of the potential anisotropy, and in particular probe the relative magnitudes of the different anisotropic terms in the potential (V3 and V4).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.464382
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...