We performed spectral hole burning experiments in the UV with p-chlorotoluene as a probe in cyclohexane. A method is presented which allows for the determination of the rotational tunneling splitting in S-0 and S-1. The respective values are (117+/-4) GHz (3.90+/-0.13) cm(-1) and (84+/-4) GHz (2.80+/-0.13) cm(-1). From these numbers the rotational barriers and the respective rotational eigenvalues can be determined. Based on these results the spin conversion dynamics is reinterpreted as being governed by Orbach processes.