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The transient absorption spectrum of eam" induced in neat liquid ammonia by nanosecond pulse radiolysis shifts to higher energies as temperature decreases. The transition energy at the absorption maximum increases from 0.67 to 0.88 eV as temperature decreases from 23 to -75°. The portion of bandwidth at halfmaximum measured from the absorption maximum to the high-energy side of the spectrum is constant over the temperature range from 23 to -75°. For the same temperature range, the primary yield of eam-is constant with a value and average deviation of 3.1 ± 0.3. The mechanism of decay of eam~i n pulse radiolysis of neat liquid ammonia is complex.

The absorption spectrum and primary yield of the solvated electron in liquid ammonia (eam−) have been determined by nanosecond pulse radiolysis of liquid ammonia at 23°C and pressures up to 6.7 kbar. With increase in pressure from 0.009 kbar (vapor pressure at 23°C) to 6.7 kbar, the following changes occur in the absorption spectrum: The transition energy at the absorption maximum (Emax) increases from 0.67 to 0.91 eV; the observable portion W of the bandwidth at half-maximum, from Emax to the high-energy side of the spectrum, increases by 35%; and optical density at the absorption maximum (ODmax) decreases by 32%. The pressure and temperature dependences of Emax are attributed to changes in (1) size of the electron cavity and (2) the local dielectric constant associated with the solvation shell of the electron. At 23°C and 0 kbar, (∂lnEmax/∂P)T for eam− exceeds that for solvated electrons in water, methanol, and ethanol by a factor of ∼4. Such a result indicates that the cavity of eam−(V̄=98 ml mol−1) is more compressible than that of the electron in water (V̄ = 7 ml mol−1 for eaq−) and the alcohols. From the changes in W and ODmax with increase in pressure from 0.009 to 6.7 kbar, the extinction coefficient at the absorption maximum is estimated to decrease by 19% (similar to the result for eaq−) and the primary yield is estimated to decrease from 3.2 to 2.0 solvated electrons per 100 eV (in contrast with invariance of the eaq− yield). The decrease in primary yield is attributed to an increase in the probability of neutralization relative to separation of geminate NH4+−eam− pairs owing to the large negative activation volume of the neutralization reaction as a consequence of the large volume of eam−.

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