A holographic technique is used to investigate the photochemical action spectrum of the second step in the two-photon photodissociation of dimethyl-s-tetrazine (DMST) in poly(vinylcarbazole) (PVK). We are able to show from these measurements that the previously observed transient absorption in the 600-700-nm spectral region is not directly involved in the second step absorption that leads to photodissociation. Furthermore, from the very fact that holograms can be produced with modest laser powers in this system, we are able to conclude that the intermediate in the second step cannot have a lifetime on the nanosecond or shorter time scale. © 1981, American Chemical Society. All rights reserved.