Excitation transfer in the radiolysis of alkanes in the solid phase at 77 K

The role of excited molecules and excitation transfer in the radiolysis of solid alkanes at 77 K is described. Studies of the effect of electron scavengers in the radiolysis of solid alkanes show that hydrogen formation is mainly due to a nonionic process. Though the yield of hydrogen in the radiolysis of solid isobutane at 77 K is not affected by the addition of N₂O or SF₆, it decreases sharply upon the addition of CCl₄. Similarly, the yield of C₄H₉ radical in the radiolysis of isobutane at 77 K is not changed by the presence of conventional electron scavengers; however, it decreases remarkably upon the addition of CCl₄ or toluene. When 2,3-dimethylbutane (23DMB) containing a small amount of toluene (To) is irradiated with γ-rays or nanosecond pulses of X-rays in the solid phase at 77 K, luminescence from excited toluene is observed. The emission spectrum from 23DMB-To (2 mol%)-N₂O(2 mol%) during γ-irradiation at 77 K is similar to that from 23DMB-To (2 mol%) during U.V.-illumination. The formation of the singlet-excited toluene is not affected by the addition of electron scavengers and hole scavengers. These results are explained by excitation transfer from alkane to additives. The possibility of exciton migration in the radiolysis of solid alkanes is discussed by a simple theoretical treatment.