Knowledge Bank

Photodissociation spectra of $CH4-C2H4,CD2H2--C2H4$, and $CD4-C2H4$ were observed by exciting the $\nu 7$ mode of ethylene in a molecular betum and measuring lost of cluster mass spectrometer signal. Spectra were fit using a two-level lineshape model and homogeneous linewidths were used to determine complex lifetimes. Although momentum gap theory predicts varying lifetimes for the three complexes based on different densities of rotational levels in the cluster fragments, the lifetimes observed are very similar: $\tau (CH4--C2H4)=1.8ps,\tau (CD2H2--C2H4)=1.8ps,andr(CD4--C2H4)=1.5ps.$