FIG. 1.

Experimental data showing the decreases in column density of pyrimidine (N_pyr) derived from the ∼1406 cm⁻¹ bands in the IR spectra measured for the three samples irradiated with (a) the 0^th order beam light, (b) the He i line, and (c) the He ii line, as well as the first-order exponential decay fits of these photo-destruction curves of pyrimidine following Eq. 1. The half-lives derived from these curves are given in Table 2.