Resonant-light absorption and the problem of observing the Kosterlitz-Thouless transition in spin-polarized atomic hydrogen adsorbed on a liquid-He surface

We discuss the conditions for the occurrence of the Kosterlitz-Thouless phase transition in spin-polarized atomic hydrogen, adsorbed on the surface of liquid He, in contact with bulk hydrogen gas. We show that the phase transition will have a marked effect on the density of adsorbed atoms. We present calculations in which we show that determination of this surface density, crucial for detecting the transition, may be done through surface selective absorption of resonant light.