Browsing by Author "Wunner, Günter"

Now showing 1 - 4 of 4

Open Access
Analysis of hydrogen Rydberg spectra in a uniform magnetic field: uncovering the transition from regularity to irregularity in a real quantum system
(1986) Wunner, Günter; Woelk, Ulrich; Zech, Ingrid; Zeller, Gudrun; Ertl, Thomas; Geyer, Florian; Steitz, Arno; Schweizer, Wolfgang; Ruder, Hanns
Studies of the behaviour of quantum systems in a range of energy where their classical counterparts undergo transitions from regularity to irregularity, as manifested in phase space by the gradual destruction of invariant tori, to date have largely been confined to model Hamiltonian systems such as harmonic oscillators with cubic, quartic, or higher-degree polynomial corrections, or the stadium problem. We show that phenomena which have turned out characteristic of the onset of "quantum stochasticity" in these model systems can in fact be recovered in the quantal energy spectra of a "real" physical system, viz. spectra of hydrogen Rydberg atoms in strong magnetic fields. This implies that one has a simple prototype system at hand in which to study - not only in theory but also in experiment, quantitatively and in detail, and as a function of a continuously tunable external parameter - phenomena that are expected to be typical of the quantum properties of nonintegrable systems in general.
Open Access
Hydrogenic Rydberg atoms in strong magnetic fields: theoretical and experimental spectra in the transition region from regularity to irregularity
(1987) Holle, Armin; Wiebusch, Gerd; Main, Jörg; Welge, Karl H.; Zeller, Gudrun; Wunner, Günter; Ertl, Thomas; Ruder, Hanns
For deuterium Rydberg atoms in a magnetic field of sim6~T we compare the complete experimental spectrum in the range -190 cm-1 to -20 cm-1 with the positions and oscillator strengths of the corresponding quantum theoretically calculated photoabsorption lines. The agreement is excellent. The range of energy covered extends from the end of thel-mixing regime up to the regions where the approximate integrability of the problem is completely lost, and the corresponding classical system undergoes a transition to chaos.
Open Access
Rydberg atoms in uniform magnetic fields: uncovering the transition from regularity to irregularity in a quantum system
(1986) Wunner, Günter; Woelk, Ulrich; Zech, Ingrid; Zeller, Gudrun; Ertl, Thomas; Geyer, Florian; Schweizer, Wolfgang; Ruder, Hanns
We investigate the eigenvalue spectra of hydrogen Rydberg atoms in strong magnetic fields for manifestations of quantum stochasticity and find (i) a smooth transition from a Poisson-type to a Wigner-type distribution of level spacings in the range of energy where classical motion becomes increasingly chaotic, (ii) the occurrence of multiple avoided crossings, and (iii) connected with this, an extreme sensitivity of oscillator strengths, and thus of observable spectra, with respect to small variations of an external parameter, viz., the magnetic field strength.
Open Access
Werner Eissner (1930-2022) : a pioneer in computational atomic physics
(2023) Bhatia, Anand K.; Lynas-Gray, Anthony E.; Mendoza, Claudio; Nahar, Sultana; Nussbaumer, Harry; Pradhan, Anil K.; Seaton, Anthony M.; Wunner, Günter; Zeippen, Claude J.