Photoelectric Franck-Hertz experiment and its kinetic analysis by Monte Carlo simulation

Abstract

The electrical characteristics of a photoelectric Franck-Hertz cell are measured in argon gas over a wide range of pressure, covering conditions where elastic collisions play an important role, as well as conditions where ionization becomes significant. Photoelectron pulses are induced by the fourth harmonic UV light of a diode-pumped Nd:YAG laser. The electron kinetics, which is far more complex compared to the naive picture of the Franck-Hertz experiment, is analyzed via Monte Carlo simulation. The computations provide the electrical characteristics of the cell, the energy and velocity distribution functions, and the transport parameters of the electrons, as well as the rate coefficients of different elementary processes. A good agreement is obtained between the cell's measured and calculated electrical characteristics, the peculiarities of which are understood by the simulation studies.

Experimental and computational investigations of electron dynamics in micro atmospheric pressure radio-frequency plasma jets operated in He/N2 mixtures

“…After being generated at the electrodes they are accelerated towards the bulk by the sheath electric field and cause excitation repeatedly. Similar to the Franck-Hertz experiment, we observe striations in the excitation patterns near the electrodes due to non-equilibrium effects of the electron transport [76][77][78][79][80][81][82]. In the spatial and temporal domains where the striations appear, the reduced electric field is within the 'window' of its values where periodic relaxation of the electron velocity distribution function (VDF) is expected [83][84][85].…”

Helium metastable species generation in atmospheric pressure RF plasma jets driven by tailored voltage waveforms in mixtures of He and N2

“…This effect is caused by electrons which after being generated at the electrodes (via secondary electron emission due to ion bombardment), are accelerated towards the bulk by the sheath electric field and cause excitation repeatedly. Based on this electrons gain and lose energy repeatedly and, thus, striations are generated, similar to the Franck-Hertz experiment [ [75][76][77][78][79]. As mentioned above, we assume that 50% of all excitation events for e − + He atom collision processes form helium metastables.…”

From macro-measure of Franck–Hertz curves to micro-collisions between electrons and argon atoms

“…In analogy to the tube made for Franck-Hertz experiments with mercury [13,14], we adopt an evacuated cylindrical shaped glass tube filled with low-pressure argon vapor at room temperature. The pressure inside the glass tube is difficult to measured and is estimated to be around a few mbar [12]. This tetrode tube, schematically shown in figure 1, is akin to an earlier described version [15].…”

“…The reproduced experiment is universal in the undergraduate laboratory, and mostly carried out with mercury [6][7][8][9] and neon [10]. Argon is the third most abundant gas in the Earth's atmosphere, and the electron impact excitation of argon atoms is found in space applications [11,12]. We reproduce the Franck-Hertz experiment on our undergraduate physics course with low-pressure argon vapor at room temperature, in which case the mean free path of the electrons remains almost unchanged, therefore the experimental results are stable.…”