Conduction electron paramagnetic resonance study of concentrated alkali metal-ammonia solutions

Peck, R; Glaunsinger, W. S.

doi:10.1016/0022-2364(81)90099-8

Cited by 4 publications

(5 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…1 MPM result from a variety of competing relaxation mechanisms (e.g. electron-electron exchange, dipolar interactions, spin-orbit coupling with the metal ion, and conduction electrons) 30,35–37 and are thus somewhat difficult to model precisely.…”

Section: Analysis and Discussionmentioning

confidence: 99%

“…37,41 For the simplest dynamic modelling of such an interaction between the excess or solvated electron and surrounding ammonia solvent shells (Figure 1), we may write:

\frac{1}{T_{1}} = \frac{1}{3} A_{eff}^{2} \frac{I (I + 1)}{N} J (ω)

\frac{1}{T_{2}} = \frac{1}{3} A_{eff}^{2} \frac{I (I + 1)}{N} \frac{J (ω) + J (0)}{2}

Thus, \frac{T_{1}}{T_{2}} = \frac{1}{2} (1 + \frac{J (0)}{J (ω)})

where I is the nuclear spin, J ( ω ) is the spectral density, N is the total effective number of solvent (NH 3 ) molecules in the various contributing solvation shells, and A eff is the total effective 14 N Fermi-contact interaction of the solvated electron with the N surrounding ammonia molecules, 24,41 in various solvation shells (Figure 1). …”

Section: Analysis and Discussionmentioning

confidence: 99%

“…It is established that electron spin relaxation processes in lithium–ammonia solutions of metal concentrations higher than ∼1 MPM result from a variety of competing relaxation mechanisms (e.g., electron–electron exchange, dipolar interactions, spin–orbit coupling with the metal ion, and conduction electrons) ,− and are thus somewhat difficult to model precisely.…”

Section: Analysis and Discussionmentioning

confidence: 99%

“…At concentrations of 0.3 MPM and below, it is recognized that electron spin relaxation is best described by a single physical process involving the modulation of the nitrogen hyperfine Fermi-contact interaction. , For the simplest dynamic modeling of such an interaction between the excess or solvated electron and surrounding ammonia solvent shells (Figure ), we may write: 1 T 1 = 1 3 A eff 2 I ( I + 1 ) N J ( ω ) 1 T 2 = 1 3 .25em A eff 2 .25em I ( I + 1 ) N J ( ω ) + J ( 0 ) 2 Thus, T 1 T 2 = 1 2 ( 1 + J false( 0 false) J false( ω false) ) where I is the nuclear spin, J (ω) is the spectral density, N is the total effective number of solvent (NH 3 ) molecules in the various contributing solvation shells, and A eff is the total effective 14 N Fermi-contact interaction of the solvated electron with th...…”

Section: Analysis and Discussionmentioning

confidence: 99%

Section: Analysis and Discussionmentioning

confidence: 99%

See 4 more Smart Citations

Electron Tunneling in Lithium–Ammonia Solutions Probed by Frequency-Dependent Electron Spin Relaxation Studies

et al. 2012

View full text Add to dashboard Cite

Electron transfer or quantum tunneling dynamics for excess or solvated electrons in dilute lithium-ammonia solutions have been studied by pulse electron paramagnetic resonance (EPR) spectroscopy at both X- (9.7 GHz) and W-band (94 GHz) frequencies. The electron spin-lattice (T1) and spin-spin (T2) relaxation data indicate an extremely fast transfer or quantum tunneling rate of the solvated electron in these solutions which serves to modulate the hyperfine (Fermi-contact) interaction with nitrogen nuclei in the solvation shells of ammonia molecules surrounding the localized, solvated electron. The donor and acceptor states of the solvated electron in these solutions are the initial and final electron solvation sites found before, and after, the transfer or tunneling process. To interpret and model our electron spin relaxation data from the two observation EPR frequencies requires a consideration of a multi-exponential correlation function. The electron transfer or tunneling process that we monitor through the correlation time of the nitrogen Fermi-contact interaction has a time scale of (1–10)×10−12 s over a temperature range 230–290K in our most dilute solution of lithium in ammonia. Two types of electron-solvent interaction mechanisms are proposed to account for our experimental findings. The dominant electron spin relaxation mechanism results from an electron tunneling process characterized by a variable donor-acceptor distance or range (consistent with such a rapidly fluctuating liquid structure) in which the solvent shell that ultimately accepts the transferring electron is formed from random, thermal fluctuations of the liquid structure in, and around, a natural hole or Bjerrum-like defect vacancy in the liquid. Following transfer and capture of the tunneling electron, further solvent-cage relaxation with a timescale of ca. 10−13 s results in a minor contribution to the electron spin relaxation times. This investigation illustrates the great potential of multi-frequency EPR measurements to interrogate the microscopic nature and dynamics of ultra fast electron transfer or quantum-tunneling processes in liquids. Our results also impact on the universal issue of the role of a host solvent (or host matrix, e.g. a semiconductor) in mediating long-range electron transfer processes and we discuss the implications of our results with a range of other materials and systems exhibiting the phenomenon of electron transfer.

show abstract

Section: Analysis and Discussionmentioning

confidence: 99%

“…37,41 For the simplest dynamic modelling of such an interaction between the excess or solvated electron and surrounding ammonia solvent shells (Figure 1), we may write: