Resolution Enhanced ESR Spectra of the Trapped Electrons in an Alkaline Ice

Ohno, Keiichi; Takemura, Isao; Sohma, Junkichi

doi:10.1063/1.1677345

Cited by 11 publications

(7 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…While the distances reported by Astashkin et al 32 broadly agree with these MQC MD estimates, their estimate for the coordination number is suspect since the predicted second moment M 2 in protiated alkaline glass 32 is 40-50% lower than observed. 28,29 Simulating the EPR spectrum of e hyd − using this 2deutron model yields a 7-line pattern resembling the one observed by Ohno et al 39 in 2-5…”

Section: Magnetic Resonance Studiessupporting

confidence: 66%

“…The first such EPR spectrum was obtained by Bennet et al by deposition of Na atoms on polycrystalline ice; 37 that was followed by studies on γ-irradiated alkaline glasses containing a relatively low fraction of NaOH. 38,39 Such glasses include numerous microscopic ice crystallites, whose fraction, size, and morphology vary from sample to sample. These crystallite inclusions seemed to improve 8.…”

Section: Magnetic Resonance Studiesmentioning

confidence: 99%

“…Because EPR spectra of the trapped electron in alkaline ices are structureless, − these spectra provide the estimate of the “total” magnetic coupling that is given by the second moment M 2 of the resonance line; the proton contribution to the latter is ∼23 G 2 in the alkaline ices (eq B5 in Appendix B). Assuming that the protons are magnetically equivalent and the coordination number n is known, these estimates can be refined using “flip-flop satellites;” 33 for n = 5, this analysis gives | a | = 2 ± 3 G and 2 T ⊥ = 8.3 ± 1 G (which corresponds to r X H ≈ 1.98 Å).…”

Section: Magnetic Resonance Studiesmentioning

confidence: 99%

“…3-5 G) were suggested by these semicontinuum models. 25,44 Since the initial EPR experiments 37,38,39 seemed to yield such large hfcc constants (see above), these experiments were considered to be supportive of such one-electron models. The subsequent ESEEM experiments, 32,33 however, yielded hfcc estimates that are clearly incompatible with these one-electron models.…”

mentioning

confidence: 99%

See 3 more Smart Citations

The Structure of the Hydrated Electron. Part 1. Magnetic Resonance of Internally Trapping Water Anions: A Density Functional Theory Study

Shkrob

2007

J. Phys. Chem. A

View full text Add to dashboard Cite

Density functional theory (DFT) is used to rationalize magnetic parameters of hydrated electron trapped in alkaline glasses as observed using Electron Paramagnetic Resonance (EPR) and Electron Spin Echo Envelope Modulation (ESEEM) spectroscopies. To this end, model water cluster anions (n=4-8 and n=20,24) that localize the electron internally are examined. It is shown that EPR parameters of such water anions (such as hyperfine coupling tensors of H/D nuclei in the water molecules) are defined mainly by the cavity size and the coordination number of the electron; the water molecules in the second solvation shell play a relatively minor role. An idealized model of hydrated electron (that is usually attributed to L. Kevan) in which six hydroxyl groups arranged in an octahedral pattern point towards the common center is shown to provide the closest match to the experimental parameters, such as isotropic and anisotropic hyperfine coupling constants for the protons (estimated from ESEEM), the second moment of the EPR spectra, and the radius of gyration. The salient feature of these DFT models is the significant transfer (10-20%) of spin density into the frontal O 2p orbitals 2.of water molecules. Spin bond polarization involving these oxygen orbitals accounts for small, negative hyperfine coupling constants for protons in hydroxyl groups that form the electron-trapping cavity. In Part 2, these results are generalized for more realistic geometries of core anions obtained using a dynamic one-electron mixed qunatum/classical molecular dynamics model.

show abstract

Section: Magnetic Resonance Studiessupporting

confidence: 66%

Section: Magnetic Resonance Studiesmentioning

confidence: 99%

Section: Magnetic Resonance Studiesmentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

The Structure of the Hydrated Electron. Part 1. Magnetic Resonance of Internally Trapping Water Anions: A Density Functional Theory Study

Shkrob

2007

J. Phys. Chem. A

View full text Add to dashboard Cite

show abstract

“…We use the results of Vincow and Johnson17 to handle contributions d and e from nearest neighbor protons. <H2)/ = np[a2/4 + (bxx2 + by2 + 222)/12] (13) where bxx, byy, and bzz are the principal values of the dipolar hyperfine coupling tensor b in the dipolar spin Hamiltonian H = i>b,.7: (14) >1 An expression similar to (13) holds for nearest neighbor deuterons, and summing nearest neighbor proton and deuteron contributions to the second moment gives (H% = <HV + <HV = («p + and)(a2/4 + 2/4) (15) where b2 » |(6«2 + byy2 + bj) (16) Summing the contributions to the second moment due to a-e above, we get S(X,«P) = (np + and)(a2l4 + b2/4) + SP""[1 -(1 -a)X] + S" (17) where S(X,np) denotes the second moment of the epr line due to et~i n a site with np nearest neighbor protons and nnp nearest neighbor deuterons at fractional deutera-tionX given by (1).…”

Section: Theorymentioning

confidence: 99%

Electron paramagnetic resonance and electron-nuclear double resonance line shape studies of trapped electrons in .gamma.-irradiated deuterium-substituted 10 M sodium hydroxide alkaline ice glass

Bales¹,

Helbert²,

Kevan³

1974

J. Phys. Chem.

View full text Add to dashboard Cite

The epr and endor line widths and line shapes for the trapped electron produced by -irradiation in alkaline ice glasses at 77 K have been studied both theoretically and experimentally as a function of matrix deuteration. The theoretical model is based on the trapped electron (et") interacting equivalently with n nearest neighbor protons and deuterons. The interactions considered include (a) dipolar contributions between et" and other radicals, (b) dipolar contributions between et" and alkali metal nuclei, (c) dipolar interactions between et" and nonnearest neighbor protons and deuterons, (d) dipolar interactions between et" and nearest neighbor protons and deuterons, and (e) Fermi contact interactions with nearest neighbor protons and deuterons. The comparison of experimental and theoretical results allow us to set bounds on n and the Fermi contact coupling a, although unique values of a and n cannot be determined.It is also shown that the dipolar hyperfine coupling must be appreciable. Both theory and experiment show that the deviation of the line shape from Gaussian is a maximum near 80% deuteration. The experimental results also show that the line widths are dependent on sample preparation methods and that this dependence appears to be associated with the freezing rate at which the matrix is formed. A simple theoretical model suggests that at slower freezing rates there is a preference for OH over OD bond orientation toward et".

show abstract