Rotationally elastic and inelastic dynamics of NO(X2Π, v = 0) in collisions with Ar

Area of Science:

• Chemical Physics
• Molecular Collisions
• Spectroscopy

Background:

• Understanding molecular collisions is crucial for chemical kinetics and atmospheric science.
• Polarization transfer in collisions influences reaction pathways and product distributions.
• Previous studies suggest differences in elastic depolarization efficiency between similar molecular systems.

Purpose of the Study:

• To investigate the depolarization of specific nitric oxide (NO) energy levels during collisions with argon (Ar).
• To compare theoretical predictions with experimental measurements of polarization loss rate constants.
• To elucidate the contributions of elastic depolarization and inelastic population transfer to total polarization loss.

Main Methods:

• Combined theoretical quantum scattering calculations and experimental two-color polarization spectroscopy.
• Extraction of rate constants for elastic depolarization (K=1, K=2) and inelastic population transfer.
• Measurement of total polarization loss rate constants for selected NO initial levels.

Main Results:

• Qualitative agreement between theory and experiment on the modest decline of polarization loss rate constants with increasing rotational quantum number (j).
• Significant quantitative discrepancies observed between theoretical and experimental absolute values for polarization loss.
• Experimental data showed no significant dependence on the rank (K) of polarization, aligning with theoretical predictions of modest elastic depolarization contribution.

Conclusions:

• Elastic depolarization is a minor contributor to the total polarization loss in NO + Ar collisions.
• The observed discrepancies between theory and experiment warrant further investigation.
• The findings reinforce that elastic depolarization is less efficient for NO + Ar compared to OH + Ar collisions.