Degeneration of the charged

These features of molecules in degenerate states should be manifest in the experiments that depend critically on the first nonzero moment of the charge distribution. 

We focus on the electronic ground state of the charged particle, ( l ) = (2 7t) and the first, degenerate, pair of excited states. 

Ideally, the specific heat of conduction electrons (or holes) in a metal is a linear function of temperature C = yT, where y, known as the Sommerfeld constant, is in the range 0.001 to 0.01 J/(molK ) for normal materials. In HF compounds, y reaches values up to 10 times larger (see tables 9, 10 and 11). In the basic theory of the specific heat of itinerant electrons (free Fermi gas), y is proportional to the effective mass m of the charge carriers, and so the name heavy fermions has come to be attached to these high-y materials (see Stewart 1984). The linear relation between C and T is strictly fulfilled only in the limit of a free degenerate electron gas. In real materials, weak non-linearities show up that can be encompassed by, for example, allowing y to be temperature dependent, y T). The Sommerfeld constant of interest is then the extrapolation of y for... 

Especially, the unique ability of pressure to investigate the influence of impurity-trapped exciton states, which are created after ionization and charge transfer transitions, on the luminescence of TM and RE ions in solids was presented. The effect relies on pressure-induced luminescence quenching and recovery if the degeneration of the emitting level with the impurity-trapped exciton state is caused or removed, respectively. 

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