We also studied the E-9/ps1 pair under ambient conditions by μs-TAS (Fig. ) and found the intensity of transient absorption at 430 nm immediately after excitation (ΔAbs * 430) to be inversely proportional to the amount of (E-9)2⊂C, consistent with the quenching of the ps1's triplet state by its E-9 co-guest via TET. The resulting triplet-9 can either relax to the initial E-9 isomer or switch to Z-9, which absorbs at 430 nm -hence the increasing steadystate absorption . This intimate relationship between the degree of ps1 triplet state quenching and the extent of E→Z isomerization identified by μs-TAS further confirms that DESC proceeds via TET between the ps1 donor and E-9 acceptor.