Ion-atom collision-induced absorption

Area of Science:

• Atomic and Molecular Physics
• Quantum Electrodynamics
• Spectroscopy

Background:

• Collision-induced absorption (CIA) is a phenomenon where atomic or molecular collisions lead to light absorption.
• Long-range electrostatic forces play a crucial role in mediating these collision-induced transitions.
• Understanding CIA is vital for interpreting spectra in various physical environments, including astrophysical and laboratory plasmas.

Purpose of the Study:

• To investigate the linear electrodynamics governing ion-atom collision-induced absorption.
• To analyze the characteristics of spectral lines produced by this process, focusing on intensity, symmetry, and width.
• To apply these principles to a specific forbidden transition in tin (Sn) induced by collisions with iodide ions (I(-)).

Main Methods:

• Theoretical examination of linear electrodynamics in the context of ion-atom collisions.
• Analysis of spectral line properties resulting from collision-induced absorption.
• Quantitative assessment of the absorption coefficient for the specific Sn-I(-) system.

Main Results:

• Collision-induced absorption via long-range electrostatic forces yields intense, symmetrical, and narrow spectral lines.
• The forbidden (3)P(0) to (1)S(0) transition in tin is effectively induced by collisions with iodide ions.
• The measured absorption coefficient is 0.45%/cm per Torr of Sn and per 0.1 Torr of I(-), with line widths around 15 cm(-1).

Conclusions:

• Ion-atom collisions provide a significant mechanism for inducing otherwise forbidden transitions.
• The observed spectral characteristics confirm the predictions of linear electrodynamics for this process.
• This research quantifies collision-induced absorption, offering valuable data for spectroscopic analysis and plasma physics.