ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

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
    Self-, N2, O2, H2, Ar, and He broadening in the ν3 band Q branch of CH4 (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 773-785 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Self-, N2-, O2-, H2-, Ar-, and He-broadening coefficients, pressure shifts, and integrated intensities have been measured for most transitions in the Q branch of the ν3 fundamental band of methane using a difference-frequency laser spectrometer. A systematic dependence of the broadening coefficients on the tetrahedral symmetry species and order index is observed with striking similarities for N2, O2, and Ar and for H2 and He buffer gases. Comparison with earlier measurements on other bands and branches of methane indicates very little vibrational, branch, or carbon isotope dependence. Dicke narrowing is evident at intermediate pressures, yielding an average narrowing coefficient and an optical diffusion constant for each gas mixture. A small amount of line mixing is evident for strongly overlapped lines near atmospheric pressure from nonlinear deviations of the observed spectra from the contours extrapolated from lower pressure measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.463943
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Molecular beam spectrum of the highly perturbed C–H stretching region of fluoroform (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 2720-2728 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Assignments of the C–H stretching fundamental of fluoroform, CHF3, have been obtained from a spectrum recorded near 3035 cm−1 at sub-Doppler resolution (∼10 MHz FWHM) and low effective temperature (∼4 K) in an adiabatically cooled molecular beam using bolometric detection of molecules excited by a color-center laser. This fundamental band is highly perturbed and has resisted analysis at higher temperatures, even at Doppler-limited resolution, whereas its overtones have been the subject of several studies of intramolecular vibrational relaxation. Under molecular beam conditions, the central Q branch, which dominates the spectrum at room temperature, almost vanishes, while the bulk of the intensity is equally shared by two "sidebands'' with Q branches symmetrically displaced by ∼±5 cm−1 from the suppressed central Q branch. This peculiar structure is due to a close anharmonic and Coriolis resonance between the fundamental ν1 (species A1) and the combinations ν±4+ν±5+ν±6 (A1+A2) located only 1.40 cm−1 above ν1, whose origin is at 3033.55 cm−1. The coupling constant of the resonance is k1456/2=3.68 cm−1. Additional severe perturbations by the E components of ν4+ν5+ν6 as well as by ν2+ν4+ν6 have been identified in the spectrum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455023
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Vibrational, rotational, and tunneling dependence of vibrational predissociation in the HF dimer (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 6636-6643 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Vibrational predissociation linewidths have been resolved in the two H–F stretching bands of the HF dimer using an optothermal (bolometer-detected) molecular-beam color-center laser spectrometer. In addition to the strong vibrational mode dependence reported earlier by several groups, we observe a substantial K-rotational and tunneling dependence to the longer-lived mode ν1, which is associated with the "free-H'' stretch. The predissociation linewidths (FWHM in MHz) for this vibration are 6.4(5) for K=0+, 9.5(5) for K=0−, 10.2(5) for K=1+, and 11.8(5) for K=1−, where the +/− superscripts refer to the symmetric/antisymmetric tunneling states. The J dependence (at low J) is negligible compared to the K dependence. The K=0 levels of the "bound-H'' stretch have tunneling-independent widths of 330(30) MHz. Extraneous broadening due to saturation effects was observed and corrected for in these measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455385
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Infrared and microwave investigations of interconversion tunneling in the acetylene dimer (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 6028-6045 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A sub-Doppler infrared spectrum of (HCCH)2 has been obtained in the region of the acetylene C–H stretching fundamental using an optothermal molecular-beam color-center laser spectrometer. Microwave spectra were obtained for the ground vibrational state using a pulsed-nozzle Fourier transform microwave spectrometer. In the infrared spectrum, both a parallel and perpendicular band are observed with the parallel band being previously assigned to a T-shaped C2v complex by Prichard, Nandi, and Muenter and the perpendicular band to a C2h complex by Bryant, Eggers, and Watts. The parallel band exhibits three Ka=0 and three asymmetry-doubled Ka=1 series. The transitions show a clear intensity alternation with Kc with two of the Ka=0 series missing every other line. In addition, the perpendicular band has the same ground-state combination differences as the parallel band. To explain these apparent anomalies in the spectrum, we invoke a model consisting of a T-shaped complex with interconversion tunneling between four isoenergetic hydrogen-bonded minima. In this picture, the parallel and perpendicular bands arise from excitation of the acetylene units parallel and perpendicular to the hydrogen bond. The observation of rotation–inversion transitions in the microwave spectrum, in addition to the pure rotation transitions of Prichard, Nandi, and Muenter, verifies the model. The measured microwave splittings yield a tunneling frequency of 2.2 GHz which is consistent with a ∼33 cm−1 barrier separating the four minima.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455417
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Vibrational predissociation in the CO2 dimer and trimer and rare gas–CO2 complexes (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 100-109 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Vibrational predissociation linewidths for the CO2 dimer and trimer and the Ne–CO2 and Ar–CO2 complexes have been resolved using a bolometer-detected (optothermal) molecular-beam color-center laser spectrometer. Observations were made on the pair of vibrations near 3715 and 3613 cm−1 corresponding to the ν1+ν3/2ν02+ν3 Fermi diad of CO2. Homogeneous linewidths of from ∼0.5 to ∼22 MHz (FWHM) were measured for these related complexes, with Ne–CO2 exhibiting both the broadest and the sharpest lines for the upper and lower bands, respectively. Ar–CO2 and (CO2)2 showed mode-independent intermediate predissociation rates while only the lower band of (CO2)3 could be found. The results indicate that V→V energy transfer processes are the dominant predissociation channels with symmetry selection or propensity rules and specific resonances playing a role.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455512
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Isotope effects in the high-resolution infrared spectrum of OC–HF (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 4147-4152 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: High-resolution infrared spectra of the H–F stretching bands of natural OC–HF and enriched O13C–HF and 18OC–HF have been recorded under thermal equilibrium conditions near 195 K with a tunable difference-frequency laser. The rotational constants of the three isotopic species are consistent with the linear C–H van der Waals bond as determined by microwave spectroscopy. The isotope shifts for the band centers exhibit a curious staggering with total CO mass which we attribute to anharmonic coupling of the zero-point CO bending motion. Resolved splittings of the l doublets in a hot band originating in the CO bending vibration yield tentative assignments and rotational constants for this low frequency van der Waals mode.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453821
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Structure and vibrational dynamics of the CO2 dimer from the sub-Doppler infrared spectrum of the 2.7 μm Fermi diad (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 2185-2195 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Sub-Doppler infrared spectra of two Fermi resonance coupled bands of carbon dioxide dimer have been obtained at 3611.5 and 3713.9 cm−1 using an optothermal molecular beam color-center laser spectrometer. The band origins for the complexes are red shifted by approximately 1 cm−1 from the corresponding ν1+ν3/2ν02+ν3 CO2 bands. The higher frequency band is perturbed while the lower frequency band appears free of extraneous perturbations as determined from a precision fit to a Watson asymmetric rotor Hamiltonian. This fit and the observed nuclear spin statistical weights reveal that the complex is planar with C2h symmetry. The C--C separation and C--C–O angle are determined to be 3.599(7) A(ring) and 58.2(8)°, respectively. The nearest neighbor O--C distance is 3.14 A(ring) which is the same as that found in the crystal. From the centrifugal distortion analysis the weak bond stretching and symmetric bending frequencies are estimated to be 32(2) and 90(1) cm−1. No interconversion tunneling is observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454051
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Optothermal-detected microwave-sideband CO2-laser spectroscopy of Ar–NH3 (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 7061-7067 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A microwave-sideband CO2-laser optothermal spectrometer with a resolution better than 1 MHz has been used to record the infrared spectrum of Ar–NH3 in the vicinity of the aR(0,0) line of the ν2 vibration of free NH3. A Π←∑ type band is observed, giving a positive l-type doubling constant q, of 90.9 MHz for the upper state. The positive q indicates that the j=1, k=0, ∑ state is above the j=1, k=0, Π state in the v2=1 excited state, where j and k specify the correlation of the internal-rotor state of the Ar–NH3 complex to the NH3 monomer rotational state j,k. The ν2 vibrationally excited complex is found to predissociate in less than the 0.9 ms transit time between the bolometer detector and laser-excitation region. A lower limit to the upper-state lifetime can be obtained from the observed linewidths, which range from 1.5 to 3 MHz (FWHM). The present results agree with and extend the previous free-jet diode-laser absorption measurements on this band.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.460239
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Decoupling in the line mixing of acetylene infrared Q branches (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 6942-6953 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Q-branch profiles of the ν1 +ν5 , ν3 +ν4 and ν2 +2ν4 +ν5 Πu –Σg combination bands in the 2.5 μm C–H stretch-bend region of acetylene have been recorded with a difference-frequency laser spectrometer at pressures from 1 to 500 Torr (0.13 to 66.7 kPa). The broadening coefficients, obtained from the ν1 +ν5 band at pressures low enough to avoid significant spectral overlap, can be well fit with empirical rotationally inelastic energy-gap scaling laws or satisfactorily modeled with semiclassical line broadening theory using known intermolecular potential parameters. At pressures when lines are overlapped, collisional interference or line mixing is manifest as a deviation of the Q-branch profiles from an additive superposition of individual transition components. However the line coupling given by the state-to-state collisional scaling laws used to fit the broadening coefficients predicts far more collisional narrowing or Q-branch collapse than is observed. We find that only about one-third of the collisions that broaden the individual lines effectively couple the lines within the f sublevel of the l-doubled excited Π vibrational state observed in the Q branch. This decoupling indicates that there is little or no propensity for preserving the vibrational angular momentum sublevel upon collision, and that elastic reorientational and dephasing collisions may also be-significant. Additionally, we find that the collisional parameters and decoupling are independent of the vibrational state despite dramatically different spectral overlaps exhibited by the three bands studied and a close Fermi resonance between the lower two vibrations. This implies that vibrational relaxation and dephasing collision rates are negligible compared with rotationally inelastic and reorientational rates and usually can be ignored for infrared spectral broadening.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459471
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Infrared and microwave spectra of OCO–HF and SCO–HF (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 1330-1336 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The H–F stretching bands of the OCO–HF and SCO–HF complexes have been studied by optothermal (bolometer-detected) molecular-beam spectroscopy. Both species exhibit spectra of a quasilinear molecule red shifted from free HF by 52.1 and 57.5 cm−1, respectively. The principal band in both molecules is accompanied by a slightly red-shifted doublet-type subsidiary band that can be interpreted as a hot band of a low frequency bending vibration or a K=1 subband of a bent molecule. Accurate doublet splittings in the ground H–F vibrational state have been measured by pulsed-nozzle Fourier-transform microwave spectroscopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456074
    Location Call Number Expected 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...