Alignment of Excited Atoms in a Gas Discharge

M. R. Atadzhanov, Eugeny N. Kotlikov, М. П. Чайка

Vasilka Steflekova, Dimo Zhechev

The degenerate Zeeman sublevels were found to contribute to the ionization in a gas discharge in accordance with their coherent state. The voltage across the discharge was monitored while the same ensemble of excited atoms was alternately self-aligned ↔ nonaligned or oriented ↔ aligned. In the latter case, the coherence was optically induced; the corresponding opto-galvanic signals, i.e. amplitude- and time-resolved ones, were compared. Each state of the ensemble of degenerate Zeeman sublevels, i.e. (self-) aligned, oriented or disordered was characterized by its own rate of ionization. Various hollow cathode discharge (HCD) media were studied, namely, Ne/As, Ne/Cu, Ne/Ni, Ne/Cd, Ne/Li and Ne/Si in the corresponding commercial HCD spectral lamps.

A. P. Kazantsev

E Jacobson

Mercury atoms are excited in a weak gas discharge to the metastable 63P2 state, forming a longitudinal alignment, which is observed in the absorption of the linearly polarised green Hg line ( lambda =5461 AA). By a pulsed RF field, transverse components of the alignment are produced additionally, giving rise to modulated absorption. During the free precession the signals decay due to depolarising collisions with mercury atoms in the ground state. The cross sections for the destruction of the alignment have been determined to be sigma 0=(262.9+or-5.2) AA2 for the longitudinal component, sigma 1=(257.8+or-7.5) AA2 for the first transverse component (modulated with the Larmor frequency) and sigma 2=(273.1+or-9.0) AA2 for the second transverse component (modulated with twice the Larmor frequency). It is emphasised that these values refer to the alignment.

R. F. Stebbings

Dimo Zhechev

The self-alignment of some Ar II levels belonging to 4p and 4d configurations excited in a hollow cathode discharge is investigated. The necessary degree of coherence in the 4d levels is obtained using high-frequency discharge excitation. The radiative lifetimes and the signal broadening constants for the argon and for charged particles are determined from the Hanle signals. The contributions of the optical and electron channels to the formation of self-alignment in the discharge are discussed.