Complex Formation in Three-Body Reactions of Cl^- with H₂.

Area of Science:

• Physical Chemistry
• Chemical Physics
• Atomic and Molecular Physics

Background:

• Understanding ion-molecule reactions is crucial for various chemical processes.
• The formation and dissociation of weakly bound complexes influence reaction dynamics.
• Low-temperature environments are relevant for interstellar chemistry and plasma physics.

Purpose of the Study:

• To measure three-body reaction rates of Cl^- with H₂.
• To investigate the formation of Cl^-(H₂) and larger clusters.
• To determine the temperature dependence and mechanism of these reactions at low temperatures.

Main Methods:

• Utilizing a linear radio-frequency wire trap to confine ions.
• Performing measurements at temperatures ranging from 10 to 26 K.
• Analyzing three-body (termolecular) rate coefficients and reverse reaction rates.

Main Results:

• Measured three-body rate coefficients follow the form aT^-1 with a = 1.12(2) × 10^-29 cm⁶ K s^-1.
• Observed formation of both Cl^-(H₂) and Cl^-(H₂)₂ clusters.
• Found reverse reaction rates proportional to the cube of hydrogen density, suggesting multi-collision dissociation.

Conclusions:

• The study provides key kinetic data for Cl^--H₂ interactions at low temperatures.
• The observed temperature dependence and dissociation mechanism offer insights into ion-cluster dynamics.
• Lower ion temperatures were achieved in the wire trap compared to other multipole traps.