Atomic structure and spectra

Cowan, R. D. The theory of atomic structure and spectra-, University of California Press Berkeley, 1981. 

R. D. Cowan, The Theory of Atomic Structure and Spectra, University of California Press, Berkeley, 1981. 

Section 5.5 Atomic Structure and Spectra-quantization of Energy... 

In the theory of atomic structure and spectra systems with periodic motion are of obvious importance. In most cases it is not the details of the orbit, but the frequencies of the motion that are important. This aspect is conveniently handled by a variation of the HJ procedure that considers suitably defined constants Jj, which form a set of n independent functions of the integration constants, otj. 

R.D. Cowan (1981) The Theory of Atomic Structure and Spectra U. of California Press, Berkeley USA G.E. Bromage (1978) The Cowan-Zealot Suite of Computer Programs for Atomic Structure Appleton Laboratory Report AL-R13 Rutherford-Appleton Laboratory, Chilton, Didcot Oxfordshire 0X11 OQX UK... 

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