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

Abstract

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.