1 research outputs found
Resonance Microwave Absorption in He II.
Microwave (MW) absorption in liquid 4He is investigated in the frequency
range of 40-200 GHz at T = 1.4 - 2.5 K. Whispering gallery of waves was
generated by a dielectric disc resonator immersed into the liquid. Resonance
absorption of MWs was detected at 180.3 GHz, which corresponds to the roton
minimum of the liquid helium excitation spectrum. The creation of a single
roton is possible because of the presence of the resonator wall which absorbs
an extra momentum. The resonance frequency is shown to decreases with
temperature in an excellent agreement with the temperature dependence of the
roton gap obtained previously in the neutron scattering experiment. The
temperature dependence of the MW absorption data indicates the anomalous
behavior near the lambda-point and displays the hysteretic character.Comment: 10pages, 8 figure