Electron thermalization in dense gases and liquids: Effect of conduction band formation

The effect, of conduction band formation on electron thermalization ranges bGP was determined from free ion yield measurements in coexisting vapors and liquids. Effects for spherelike (methane) and rodlike (ethane) molecules were compared. The density range was 0.14 ≲ d/dc ≲ 2.8. The density normalized range bGPd is inversely related to the energy loss cross section of epithermal (∼0.1–1 eV) electrons. At the lower densities bGPd = 5.5 × 10⁻⁶ kg/m² in methane and ethane. In the denser gases at d/dc ≳ 0.3, bGPd increases slightly in each gas. A drastic change occurs with conduction band formation at d/dc > 1.0; bGPd in liquid methane increases to ∼4 times the value in liquid ethane. The conduction band has little net effect when the molecules are rodlike, but epithermal electron energy losses are ∼4 times less efficient in the conduction band when the molecules are spherelike.