Photoejection of Electrons from Bubble States in Liquid Helium

Electrons in Liquid Helium

“…77) Is there a connection between the fission process and the increase in mobility that is seen when bubbles in helium are illuminated with light of the right wavelength to excite optical transitions? Northby and Sanders 18) noted that the mobility enhancement was observed only for fields greater than about 1 kV cm À1 at 1.3 K, and suggested that it ''may involve the interaction of the ion with turbulence or viscosity''. A field of 1 kV cm À1 at this temperature should give a velocity 80) of around 6 m s À1 , much less than the critical velocity at which an electron bubble nucleates vortices, so it is not clear why the mobility enhancement occurs only above this field strength.…”

“…It was proposed that this change in mobility comes about because before illumination the electron bubbles are trapped on quantized vortices, and that the excitation of the electrons enables them to escape. 18,19,22) We discuss this mechanism in more detail in §6. The first experiments in which the optical absorption was observed by direct measurement were performed by Grimes and Adams 23) and by Pereversev and Parshin.…”

“…It is hard to have a high density of electron bubbles because even in the absence of an applied electric field, the space charge drives the electrons to the walls of the cell. The first measurements [18][19][20][21] did not measure the absorption directly. It was discovered that when electron bubbles were illuminated with light of the correct wavelength to excite the electron, there was a change in the mobility of the bubbles.…”

Electron Emission in Superfluid and Low Temperature Vapor Phase Helium

“…Phenomena such as two-dimensional electron gases on the surface of liquid helium, Wigner crystallization [3,4] and quantum melting [5], single-electron bubbles [6,7], multi-electron bubbles [8], electrical discharge and breakdown, etc. continue to reveal fascinating properties with unusual explanations.…”

Atomic and molecular spectra of normal liquid 4He excited by corona discharges

“…As a consequence the surrounding helium atoms are pushed away within a short time [9,10] creating a cavity around the * He and * 2 He [11], which is often referred as a "bubble" and which has typical radii between 10 and 20 Å depending on the electron's orbital radius [12]. Bubbles of similar type are well known to enclose electrons in liquid [13] and even dense gaseous helium [14]. Within the confinement of these cavities the perturbation by surrounding ground state helium atoms is low and the electronic life time of the excited atoms or excimers is almost similarly long as for free species in the vacuum.…”