An experimental and theoretical analysis is reported for the geometrical st
ructure and unpaired spin density of the CH2-NH2 radical produced in a gamm
a-irradiated single crystal of glycine at room temperature. Geometrical par
ameters obtained by using the two-center dipole approximation indicate that
the radical is not planar at the carbon site. Ab initio calculations were
performed in order to estimate the structural parameters and unpaired spin
density of the radical (C) over dot H-2-NH2 in an anisotropic matrix. A goo
d agreement was obtained between the calculated and observed values. Using
the Saturation Recovery (SR) method in the temperature range 190-290 K we h
ave obtained a set of spin lattice relaxation times, attributed to the reor
ientation of the amino group of the NH3-(C) over dot H-COO- radical, simult
aneously produced in gamma-irradiated solid glycine with (C) over dot H-2-C
OO- and (C) over dot H-2-NH2 radicals. (C) 1999 Elsevier Science B.V. All r
ights reserved.