Multiphoton processes of CO at 230 nm

Area of Science:

• Molecular Physics
• Chemical Physics
• Quantum Chemistry

Background:

• Multiphoton ionization and dissociation (MPID) of small molecules provide insights into molecular structure and dynamics.
• Carbon monoxide (CO) is a fundamental molecule for studying ionization and dissociation processes.
• Understanding fragment ion dynamics is crucial for various applications, including spectroscopy and plasma physics.

Purpose of the Study:

• To investigate the high-resolution kinetic energy release (KER) and angular distributions of C(+) and O(+) fragments from CO multiphoton ionization.
• To elucidate the dissociation dynamics of specific vibrational levels of the CO cation (CO(+)) following resonant two-photon excitation.
• To explore the influence of accidental resonances on fragment ion angular distributions.

Main Methods:

• Resonant two-photon excitation of CO to the B (1)Sigma(+) state around 230 nm.
• Multiphoton ionization followed by dissociation of CO(+).
• DC slice and Megapixel ion imaging techniques to acquire high-quality ion images.
• Analysis of kinetic energy release spectra and angular distributions of C(+) and O(+) fragments.

Main Results:

• Identified 5- and 6-photon processes contributing to C(+) and O(+) production.
• Assigned major spectral features to the dissociation of specific vibrational levels of CO(+)(X (2)Sigma(+)).
• Observed distinct angular distributions for C(+) and O(+) fragments, with variations within C(+) features.
• Attributed a dramatic change in C(+) angular distribution to an accidental one-photon resonance between CO(+)(X (2)Sigma(+), nu(+) = 1) and CO(+)(B (2)Sigma(+), nu(+) = 0).

Conclusions:

• The study reveals detailed insights into the dissociation dynamics of CO(+) following multiphoton excitation.
• Accidental resonances play a significant role in influencing fragment ion angular distributions.
• The combination of KER spectra and angular distributions provides a powerful tool for understanding underlying molecular dynamics.