The nanosecond pulse radiolysis of solutions of biphenyl in isopentane at -120°C

The yields of ions, triplet and excited singlet states of biphenyl produced in the nanosecond pulse radiolysis of 2 mmol dm3 biphenyl in iso-pentane have been measured at 20°C and −120°C. At −120°C emissions from two excited states were observed. One (peaks ca. 315 nm) appears within 1 ns of the energy input, has τ12 = 24 ns and is form the known excited singlet state of biphenyl. From the yields of ions and excited states it is concluded that the latter (singlet and triplet) are formed in the neutralization of Ph2− by solvent cations. The delayed emission (peak 380 nm) which, unlike that at 315 nm, does not appear at 20°C, shows maximum intensity at ca. 30 ns after the pulse and persists for at least 10 μs. Its intensity correlates in time with the rate of the reaction Ph2+ + Ph2−. The ion decay kinetics in the spur compare favourably with recent derivations based on scavenger studies.