Probing rotational relaxation in HBr (v=1) using double resonance spectroscopy

Area of Science:

• Chemical Physics
• Molecular Spectroscopy
• Collision Dynamics

Background:

• Understanding molecular collisions is crucial for chemical kinetics and atmospheric science.
• Rotational energy transfer (RET) plays a significant role in the relaxation of excited molecules.

Purpose of the Study:

• To investigate rotational energy transfer in hydrogen bromide (HBr) collisions.
• To determine state-to-state rate constants for collision-induced population transfer in HBr(v=1)+HBr systems.

Main Methods:

• Utilized an optical pump-probe double resonance technique.
• Employed stimulated Raman pumping for state-selective excitation of HBr(v=1) rotational levels (J=0-9).
• Monitored population evolution using (2+1) resonantly enhanced multiphoton ionization spectroscopy.

Main Results:

• Observed collision-induced population transfer with DeltaJ up to 8 at 0.32 Torr.
• Measured state-to-field rate constants for population loss ranging from 8.3x10^-10 to 4.9x10^-10 cm^3 s^-1.
• Analyzed state-to-state rate constants by fitting to numerical solutions of relaxation dynamics.

Conclusions:

• The rate coefficients for rotational energy transfer in HBr(v=1)+HBr collisions are well-represented by the statistical power exponential gap law.
• This provides valuable data for modeling chemical processes involving HBr.
• The study demonstrates the effectiveness of the pump-probe double resonance technique for studying RET.