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 of the methyl group in S0 and S1. The respective values are (117 +/- 4) GHz and (84 +/- 4) GHz. From these numbers the rotational barriers and the respective rotational eigenvalues can be determined. Based on these results the spin conversion dynamics can be doubtlessly interpreted as being governed by Orbach Processes.
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