Measurements of Lifetimes and Quenching Cross Sections of the B 3Π0u+ State of Iodine Using a Tunable Dye Laser

Lifetimes and self‐quenching cross sections of selected vibrational levels from $\text{υ′\hspace{0.17em}=\hspace{0.17em}0–25}$ of the $B^3{\Pi }_{\text{0u}}^{+}$ state of I₂ were measured from the direct decay of fluorescence excited by a pulsed, tunable dye laser. Large variations with $\mathrm{\upsilon \prime }$ of lifetimes and quenching cross sections were observed. Lifetimes changed by a factor of 3; for $\text{υ′\hspace{0.17em}=\hspace{0.17em}10}\mathrm{to}13$ , lifetimes were 1.5 μsec while for $\text{υ′\hspace{0.17em}=\hspace{0.17em}4}$ the lifetime was 0.53 μsec. This $\mathrm{\upsilon \prime }$ dependence is much larger than the calculated dependence of radiative lifetimes but can be explained by spontaneous predissociation through dissociative states crossing the $B$ state. Smaller quenching cross sections were observed for the vibrational levels with longer lifetimes.