Thermal emission from electron bubbles

An electron bubble approaching the liquid/vapor interface under the influence of an externally applied electric field experiences a potential which is the superposition of image potential and external potential. The image potential in the liquid at the liquid/vapor interface (x = 0) is given by Equation 2. For an electric field normal to the surface the potential is 

The total potential, 0(x), acting on the electron is the sum of and such that 

The electron escape rate, v, can be calculated by means of Smoluchowski s equation (Chandrasekhar, 1943), 

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The second derivative of Vq at the surface has to be estimated from experimental data. The thermal emission from bubble states in liquid helium and liquid neon have been studied in detail by Schoepe and Rayfield (1971 1973) and by Bruschi et al. (1975). The temporal decay of the emission current into the vapor space from electron bubbles imder the surface of liquid helium is shown in Figure 17. 

The optoacoustic properties of plasmon-resonant gold nanoparticles originate from photoinduced cavitation effects. This process can be summarized as follows (i) thermalization of conduction electrons on the subpicosecond timescale/ (ii) electron-phonon relaxation on the picosecond timescale and thermalization of the phonon lattice, with a subsequent rise in temperature by hundreds to thousands of degrees (iii) transient microbubble expansion upon reaching the kinetic spinodal of the superheated medium, initiated on the nanosecond timescale (iv) microbubble collapse, resulting in shockwaves and other forms of acoustic emission. The expansion and collapse of a cavitation bubble takes place on a microsecond timescale, and are easily detected by ultrasonic transducers. 

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