Study of electronically excited carbon atoms, C(21D2), by the attenuation of atomic emission, (31P °1→21D2). Part 1.—Collisional deactivation of C(21D2) by the noble gases

Abstract

Electronically excited carbon atoms C(2¹D₂) generated by the flash photolysis of carbon suboxide in the vacuum ultra-violet, have been monitored photoelectrically by attenuation of the atomic emission at λ= 193.1 nm (3¹P^°₁→2¹D₂) from a microwave-powered atomic lamp. The decay of these optically metastable atoms has been measured in the presence of the noble gases, and the following rate constants for the collisional deactivation to the electronic ground state C(2³P_J) are reported (k in cm³ molecule^–1 s^–1; 300 K): Xe, 1.1±0.3 × 10^–10; Kr, 9.4±1.6 × 10^–13; Ar, ≲ 10^–15; Ne, 1.1±0.4 × 10^–15; He, < 3 × 10^–15. The probabilities for the electronic to translational energy transfer are discussed in terms of a curve-crossing mechanism and the influence of the spin-orbit interaction on collision.