Abstract:

The energy transfer processes between ~(12)CO(A~1Π) and ~(13)CO(X ~1Σ~+) were studied at 77 K by using the technique of two-color resonance enhanced multiphoton ionization spectroscopy. In a static cell with a mixture of 0.92 ~(13)CO + 0.08 ~(12)CO, ~(12)CO molecules were populated to the A state by 2-photon excitation using an UV dye laser. The ~(13)CO(A) resulted from the collision E-E energy transfer were detected by CO(A)→CO(B)→CO~+(X) 2-step ionization using a visible dye laser. The energy transfer processes were found to be very fast with total cross sections of 1.14±0.42, 0.22±0.04, 0.17±0.06 nm for ~(12)CO(A)V=1,2,3 respectively. We found that for different vibrational channels, cross section decreases with increasing energy mismatch ΔE. Another interesting result is that, for the ∧ doublet, the production of П~+ is always larger than that of П~-. The formation of an intermediate exciplex [OCCO]* is proposed to explain the experimental results.