Rotational alignment of NO (A2Σ+) from collisions with Ne

Area of Science:

• Chemical Physics
• Molecular Dynamics
• Atomic and Molecular Collisions

Background:

• Understanding molecular alignment after collisions is crucial for chemical reaction dynamics.
• Electronically excited molecules present unique challenges due to their short lifetimes.
• Direct measurement of collision-induced alignment provides stringent tests for theoretical models.

Purpose of the Study:

• To directly measure the angle-resolved collision-induced alignment of electronically excited NO molecules.
• To investigate the rotational excitation of NO in A(2)Σ(+) state following collisions with Ne atoms.
• To compare experimental results with classical and quantum scattering calculations to assess potential energy surfaces (PES).

Main Methods:

• Utilized crossed atomic and molecular beams technique.
• Employed velocity-mapped ion imaging for precise measurements.
• Prepared NO in the A(2)Σ(+) (v = 0, N = 0, j = 0.5) state.
• Analyzed alignment using orthogonal linear probe laser polarizations for final rotational states N' = 4, 5, 7, and 9.

Main Results:

• Experimentally determined the degree of alignment induced by collisional rotational excitation.
• Observed scattering-angle dependent polarization sensitivity, with overall trends matching classical models.
• Identified structure in scattering-angle dependence not captured by classical models.
• Quantum scattering calculations qualitatively reproduced the observed structure.

Conclusions:

• Experimental measurements demonstrate sensitivity to critique ab initio potential energy surfaces for excited NO.
• The observed alignment structure provides a benchmark for theoretical methods.
• This technique offers a sensitive probe for excited-state molecular dynamics, contrasting with ground-state studies.