GLORIA

GEOMAR Library Ocean Research Information Access

X

Your email was sent successfully. Check your inbox.

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

Proceed reservation?

Export
  • 1
    Online Resource
    Online Resource
    Molecular and applied modulation effects in electron electron double resonance. V. Passage effects in high resolution frequency and field swept ELDOR
    AIP Publishing ; 1975
    In:  The Journal of Chemical Physics Vol. 62, No. 11 ( 1975-06-01), p. 4332-4342
    Details
    In: The Journal of Chemical Physics, AIP Publishing, Vol. 62, No. 11 ( 1975-06-01), p. 4332-4342
    Abstract: The observation of electron electron double resonance (ELDOR) linewidths for nitroxide radicals which are significantly less than the hyperfine envelope widths is reported. For a 1.5×10−3M solution of 2,2,6,6-tetramethyl-4-piperidinol-1-oxyl (TANOL) in sec-butylbenzene (SBB) between the temperatures of −40 °C and −70 °C, the ELDOR linewidths correspond to single spin packet widths determined by the effective electron spin–spin relaxation rates. An analysis of the precise dependence of frequency swept absorption and dispersion ELDOR signals upon microwave radiation field intensities and upon the details of the applied Zeeman modulation and accompanying phase-sensitive detection is also presented. Quantitative prediction of molecular and applied modulation effects is accomplished employing a modified density matrix treatment. Best fit parameters for TANOL in SBB at −63 °C include we(0) = 1.75×105 Hz, Te1e(0) = 1.3×10−6 sec, Te2e(0) = 2.7×10−7 sec, wn(14N) = 2.6×105 Hz, wn(all 1H) = 0 Hz, τ2 = 2×10−10 sec, ? = 2.00587, g∥ = gzz = 2.00210, g⊥ = (1/2)(gxx + gyy) = 2.00775, ? (14N) = 43.235 MHz, A∥(14N) = Azz = 92.65 MHz, A⊥(14N) = (1/2)(Axx + Ayy) = 18.53 MHz, ? (1H,axial CH3) = 1.28 MHz, ? (1H,axial CH2) = 1.57 MHz, ? (1H,equatorial CH2) = 0.84 MHz, ? (1H,all other) = 0. The theoretical and experimental results afford crucial insight into the design and performance of ELDOR experiments for optimum sensitivity in the determination of spectroscopic parameters and molecular relaxation rates.
    Type of Medium: Online Resource
    ISSN: 0021-9606 , 1089-7690
    URL: Article
    DOI: 10.1063/1.431003
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1975
    detail.hit.zdb_id: 3113-6
    detail.hit.zdb_id: 1473050-9
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 2
    Online Resource
    Online Resource
    Hot muonium and muon spur processes in nitrogen and ethane
    AIP Publishing ; 1991
    In:  The Journal of Chemical Physics Vol. 94, No. 2 ( 1991-01-15), p. 1046-1059
    Details
    In: The Journal of Chemical Physics, AIP Publishing, Vol. 94, No. 2 ( 1991-01-15), p. 1046-1059
    Abstract: Muon polarizations are reported for nitrogen and ethane over a wide pressure range from below 1 to 200 atm for N2 and up to 245 atm for C2H6. The N2 measurements were made at ambient temperature, while those for C2H6 were made at temperatures both above and below the critical temperature (305.3 K). This is the first μSR study of muonium and diamagnetic muon formation to cover the entire range from a low pressure gas to densities typical of liquids. The data are discussed in terms of hot atom and spur models. In the lowest pressure range, below 1.5 atm for N2 and about 10 atm for C2H6, the muonium polarization increases with pressure. This is well understood in terms of epithermal charge exchange. In N2 there is a small diamagnetic fraction, which is ascribed to the N2Mu+ molecular ion. This fraction approaches zero as the pressure is increased to 200 atm, with a corresponding increase in the muonium fraction, consistent with charge neutralization of the molecular ion by electrons from the radiolysis track. In C2H6, there is a decrease in the muonium fraction and a concomitant increase of the diamagnetic fraction with density, the changes occurring in two stages. The initial change is explained by stabilization of the vibrationally excited substitution products of hot muonium reactions. The second one is explained by proton transfer from the molecular ion adduct, C2H6Mu++C2H6→C2H5Mu+C2H+7, trapping the muon in a diamagnetic product. Both N2 and C2H6 have a missing fraction of polarization above 10 atm, most likely due to spin exchange of Mu with paramagnetic species created in the muon track. In N2, the missing fraction is recovered at pressures beyond about 150 atm, which is explained by scavenging of electrons by positive ions. In C2H6 the missing fraction is roughly constant for densities beyond 5 mol ℓ−1 (≊50 atm), and about twice the maximum found for N2. Both facts are consistent with the existence of ethyl radicals and hydrogen atoms in C2H6, which are longer lived than the spur electrons.
    Type of Medium: Online Resource
    ISSN: 0021-9606 , 1089-7690
    URL: Article
    DOI: 10.1063/1.460061
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1991
    detail.hit.zdb_id: 3113-6
    detail.hit.zdb_id: 1473050-9
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 3
    Online Resource
    Online Resource
    Isotope and temperature effects on the hyperfine interaction of atomic hydrogen in liquid water and in ice
    AIP Publishing ; 1995
    In:  The Journal of Chemical Physics Vol. 102, No. 15 ( 1995-04-15), p. 5989-5997
    Details
    In: The Journal of Chemical Physics, AIP Publishing, Vol. 102, No. 15 ( 1995-04-15), p. 5989-5997
    Abstract: The Fermi contact hyperfine interaction of hydrogen isotopes in liquid and solid water is below the vacuum value, shows a mass dependence, and has a negative temperature coefficient in the liquid. Furthermore, it shows a pronounced solvent isotope effect in H2O/D2O mixtures. This behavior is analyzed in terms of Dalgarno–Lewis perturbation theory for the atom in a spherical parabolic solvent potential and with a phenomenological model for spin delocalization onto solvent molecules. The results support previous suggestions that hydrogen atoms induce clathrate-like cages in liquid water. These may resemble the static structures of noble gas clathrates except that they are of transient dynamic nature in liquid water.
    Type of Medium: Online Resource
    ISSN: 0021-9606 , 1089-7690
    URL: Article
    DOI: 10.1063/1.469333
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1995
    detail.hit.zdb_id: 3113-6
    detail.hit.zdb_id: 1473050-9
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 4
    Online Resource
    Online Resource
    Spin relaxation of muonium-substituted ethyl radicals (MuCH2ĊH2) in the gas phase
    AIP Publishing ; 1996
    In:  The Journal of Chemical Physics Vol. 105, No. 17 ( 1996-11-01), p. 7517-7535
    Details
    In: The Journal of Chemical Physics, AIP Publishing, Vol. 105, No. 17 ( 1996-11-01), p. 7517-7535
    Abstract: The spin relaxation of the muonium-substituted ethyl radical (MuCH2ĊH2) and its deuterated analog (MuCD2ĊD2) has been studied in the gas phase in both transverse and longitudinal magnetic fields spanning the range ∼0.5–35 kG, over a pressure range from ∼1–16 atm at ambient temperature. The Mu13CH213ĊH2 radical has also been investigated, at 2.7 atm. For comparison, some data is also reported for the MuCH2Ċ(CH3)2 (Mu-t-butyl) radical at a pressure of 2.6 atm. This experiment establishes the importance of the μSR technique in studying spin relaxation phenomena of polyatomic radicals in the gas phase, where equivalent ESR data is sparse or nonexistent. Both T1 (longitudinal) and T2 (transverse) μSR relaxation rates are reported and interpreted with a phenomenological model. Relaxation results from fluctuating terms in the spin Hamiltonian, inducing transitions between the eigenstates assumed from an isotropic hyperfine interaction. Low-field relaxation is primarily due to the electron, via both the nuclear hyperfine (S⋅A⋅I) and the spin rotation interactions (S⋅J), communicated to the muon via the isotropic muon–electron hyperfine interaction. At the highest fields, direct spin flips of the muon become important, due to fluctuations in the anisotropic part of the muon–electron hyperfine interaction. In the intermediate field region a muon–electron ‘‘flip–flop’’ relaxation mechanism dominates, due partly to the anisotropic hyperfine interaction and partly to modulation of the isotropic muon–electron hyperfine coupling. In the case of the T2 rates, electron relaxation mechanisms dominate over a much wider field range than for the T1 rates, and inhomogeneous line broadening also contributes. The fluctuations that induce both the T1 and T2 relaxation rates are described by a single correlation time, τc, inversely proportional to the pressure. An effective spin-reorientation cross section is deduced from this pressure dependence, σJ∼100±20 Å2, for all isotopically substituted ethyl radicals. This is similar to the geometrical cross section, but about a factor of 4 larger than values of σJ found for similar-sized diamagnetic molecules by gas phase NMR, primarily reflecting the longer range of the electron-induced intermolecular potential.
    Type of Medium: Online Resource
    ISSN: 0021-9606 , 1089-7690
    URL: Article
    DOI: 10.1063/1.472578
    Language: English
    Publisher: AIP Publishing
    Publication Date: 1996
    detail.hit.zdb_id: 3113-6
    detail.hit.zdb_id: 1473050-9
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...