Kinetic Investigation of (a) the Collisional Quenching of Mg(3³P_J) by CO₂ over the Temperature Range 600–1100 K by Time‐Resolved Atomic Emission (Mg(3³P₁) → Mg(3¹S₀) + hv) and (b), E—(E, V) Transfer from Mg(3³P_J) to MgO by Time‐Resolved Molecular Emission (MgO, B¹Σ⁺ ‐ A¹II and B¹Σ⁺ ‐ X¹Σ⁺) Following Pulsed Dye‐La

Abstract

We present a kinetic study of the collisional behaviour of Mg(33PJ) with CO2 and electronic energy transfer between Mg(33PJ) and MgO over the temperature range 600–1100 K. Mg(33P1) was generated by the pulsed dye‐laser excitation of magnesium vapour in a slow‐flow system at λ = 457.1 nm (Mg(33P1) → Mg(31S0)) and monitored by time‐resolved atomic emission at the resonance wavelength using pre‐trigger photomultiplier gating with Boxcar integration and computer interfacing. Absolute second‐order rate constants were measured for the removal of Mg(33PJ) by CO2, yielding the Arrhenius form: k1 = (2.4 ±0.50.7)·10−10 exp (−(47.6±5.8 kJ mol−1)/RT) cm3 molecule−1s−1. Chemiluminescence was monitored in the time‐domain for MgO, B1Σ+ ‐ A1∏ and B1Σ+ ‐ X1Σ+) for a number of vibrational levels. The molecular emission profiles were shown to be quantitatively consistent with electronic energy transfer from Mg(33PJ) to MgO, (X1Σ+ ‐ A1∏ yielding B1Σ+) yielding MgO(B1Σ+) by correlation of the atomic and molecular emission profiles. These measurements thus demonstrate the use of the B—A and B—X band systems of MgO in the time‐domain as spectroscopic markers for the kinetic behaviour of Mg(33P1), an aspect of the observations considered in detail. Vibrational temperatures were also measured for MgO(B1Σ+) using emission from vibrational levels ν′ = 0 to 4, demonstrating significant vibrational excitation on electronic energy exchange between Mg(33P1) and MgO(X1Σ+).