Experimental observation of enhanced electron cyclotron resonance heating and nonlocal electron kinetics induced by Ramsauer-Townsend effect in ultralow electron temperature plasmas

The effect of the Ramsauer-Townsend effect, a quantum mechanical phenomenon, is investigated by generating an ultralow electron temperature plasma (T_{e}<1 eV) in a weakly magnetized inductively coupled argon plasma using a dc-biased grid. In the ultralow electron energy regime, the Ramsauer-Townsend effect is maximized, significantly reducing electron-neutral collisions. Consequently, electron cyclotron resonance (ECR) heating remains effective even at high pressures (ω_{c}≪ν), where it is typically suppressed. The enhanced ECR heating leads to a remarkable increase in electron temperature from 0.43 to 1.1 eV. Furthermore, electrons exhibit nonlocal kinetics due to the Ramsauer-Townsend effect even under the condition where local electron kinetic behavior is generally expected. These results demonstrate that quantum scattering can sustain collisionlesslike ECR heating even in highly collisional plasmas, offering insights into plasma physics and transport, crucial for advanced quantum device fabrication.