Production of Metastable Mercury Atoms by Electron Impact

Abstract

Excitation of Hg atoms by electron impact, particularly into metastable states, was studied in the energy range 4 to 15 eV. The excitation function for the 6 3 P 2 metastable state (5.46 eV) was measured from threshold up to 8.5 eV. The absolute cross-sectional scale for this state was calibrated by monitoring slow inelastically scattered electrons near threshold. The cross section had a maximum value of 3.2 x l(T 16 cm 2 ± 25% (rms) at 5.75 eV and dropped to half this value at about 8 eV. An electron beam of 0.1-eV half-width was produced by the Retarding Potential Difference RPD method. Excited atoms were detected by electron ejection from a tungsten surface. The secondary electron yield for the 6 2 P 2 state was typically 2 x 10"" 4 . Pronounced structure in the detector current with maxima at 9.00 and 9.60 eV was attributed to the 7 3 Pj state (8.64 eV). It appears that the contribution of the 6p' 3 Z> 3° metastable state was minor. An upper limit of a few times 10" 18 cm 2 was estimated for the maximum cross section of this state. Another region of structure in the total detector current occurred close to and above ionization threshold. Experimental evidence indicates that this structure was produced by long-lived auto-ionizing states.

Resonances in the electron impact excitation of metastable states of mercury

“…3. At 5.47 eV the excitation of the 6 3p~ state sets in which gives rise to a steep increase of metastable production in agreement with [3,8,10,12,14]. Probably this dramatic increase is due to the decay of the negative ion state at 5.51 eV observed by several workers e.g.…”

Measurements of electron impact optical excitation functions

“…The excitation function of the combined metastable states has been measured by Borst (1974) to 50 eV and by Mason and Newell (1987) to 142 eV. Both these measurements were made by a time-of-flight technique and the shapes of the excitation functions agree well.…”

“…Their data extend to 150 eV and are normalized to measurements over a smaller range of energies by Borst (1974). Marusin (1970, 1975) …”

“…Both these measurements were made by a time-of-flight technique and the shapes of the excitation functions agree well. Borst (1974) established an absolute scale by two independent methods, and Mason and Newell (1987) normalized their data to this. Mityureva and Smirnov (1985) measured the excitation functions for the two metastable states separately, measuring the concentration of atoms in the two states by absorption of light from a hollow cathode lamp.…”

lonization and quenching of excited atoms with the production of fast electrons

“…Для калибровки этой кривой, полученной в [92], была использована приведенная выше кон-станта скорости реакции. Величина сечения в макси-муме при ε = 5,6 эВ составляет 2,2 · 10 -16 см 2 , что несколько ниже соответствующего сечения, изме-ренного в работе [93 ] 7. Влияние процессов с образованием быстрых электронов на свойства плазмы.…”