Abstract

Rate constants for total removal of CH(A2Δ) and CH(B2∑−) in collisions with ketene were measured. For the A2Δ state, rate constants increased with vibrational quantum number; measured values were (4.5 ± 0.5) × 10^-10 cm³ molec^-1 s^-1 and (8.0 ± 1) × 10^-01 cm³ molec^-1 s^-1 for v′ = 0 and v′ = 2 respectively. For v′ = 0, rotational levels with quantum numbers from N′ = 4 to N′ = 16 were removed with similar rates within experimental errors; collisional disappearance of levels with higher rotational quantum numbers was faster for a factor of about 1.4. Calculations of cross sections for ketene and other fast colliders, assuming a multipole model, obtained a qualitative correlation with experimental values. CH(B2∑−) was more efficiently removed than CH(A2Δ, v′ = 0); for the lowest rotational levels a rate constant of (5.8 ± 0.3) × 10^-10 cm³ molec^-1 s^-1 was measured and a moderate increase with rotational quantum number was observed.