Hategan, Cornel; Ionescu, Remus Amilcar; Wolter, Hermann H.
(2020):
Siegert state approach to quantum defect theory.
In: European Physical Journal D, Vol. 74, No. 4

Full text not available from 'Open Access LMU'.
Abstract
The Siegert states are approached in framework of BlochLaneRobson formalism for quantum collisions. The Siegert state is not described by a pole of Wigner Rmatrix but rather by the equation 1  RnnLn = 0, relating Rmatrix element Rnn to decay channel logarithmic derivative Ln. Extension of Siegert state equation to multichannel system results in the replacement of channel R matrix element Rnn by its reduced counterpart Rnn. One proves the Siegert state is a pole, (1  RnnLn)(1), of multichannel collision matrix. The Siegert equation 1  RnnLn = 0, (n  Rydberg channel), implies basic results of Quantum Defect Theory as Seaton's theorem, complex quantum defect, channel resonances and threshold continuity of averaged multichannel collision matrix elements.