Mechanism of the gas-phase Cd·NH*3 complex emission

The kinetics of the CdNH*3 430 nm emission band at 550 K have been investigated by phase-shift, laser-fluorescence and steady-illumination techniques. The phase-shift measurements give values of 1.7 × 10–5 s–1 for the radiative lifetime of CdNH*3 and 9.1 × 10–13 cm3 molecule–1 s–1 for the rate constant of the process CdNH*3+ NH3→ CdNH†3+ NH3 where CdNH†3 is an unstabilized complex having a lifetime in the range 10–9–10–13 s with respect to dissociation to NH3 plus either Cd(3P1) or Cd(3P0). The laser-fluorescence measurements give values of 2.1 × 10–11 and 8.7 × 10–11 cm3 molecule–1 s–1 for the rate constants of the processes Cd(3P0)+ NH3→ CdNH†3 and Cd(3P1)+ NH3→ CdNH†3 respectively. The steady-illumination measurements show that excited states of Cd2 provide an additional energy reservoir in this system at low NH3 pressures, and imply that a species Cd†2 exists with a dissociative lifetime two or three orders of magnitude greater than that of CdNH†3.