Laser-induced photoconductivity in non-polar solutions of TMPD

Transient photoconductivity is observed when non-polar solutions of TMPD (N,N.N'.N' tetramethyl-p-phenylenediamine) are excited by the 3371 angstrom line of a pulsed nitrogen laser. The effects of pulse intensity and TMPD concentration suggest a mechanism involving the consecutive absorption of two photons, rather than one in which two monophotonic excited states interact. The effect of added piperylene indicates that the absorption of a second photon by the triplet state of TMPD accounts for approximate to 50% of the observed photocurrent. It is also suggested that light absorption by the lowest excited singlet state may account for the rest of the effect.