Thermal state distributions deduced from (2 + 1) resonance enhanced multiphoton ionization of CO

We have recently compared the (2 + 1) resonance enhanced multiphoton ionization spectra of neutral CO products desorbed from CaCO3 following pulsed UV excitation with those obtained from thermal (295 K) CO samples under similar low pressure and identical ionization conditions. As a result of this investigation, we have concluded that fitting the unresolved B-X (0-0) Q-band may lead to spurious temperature assignments with erroneous ‘hotter’ temperatures ΔT > 60 K assigned for product state distributions. Conversely, partially resolved Doppler-limited spectra are found to allow temperature assignments to within 10 K. This discrepancy may arise from line strength perturbation phenomena.