Features of the quasienergy spectrum of the hydrogen atom in a microwave field

The nearest neighbour level spacing of the quasienergies of a hydrogen atom in a micro-wave field is studied. There is evidence of level repulsion among states corresponding to classically chaotic regions. In the regions of classical phase space where the motion is approximately regular, the corresponding quasienergy spectrum can be understood in terms of approximate dynamical constants. In particular, grouping the high lying quasienergy states into photons yields level spacing plots that are close to δ functions; there is little fluctuation about the average value predicted by the approximate constant. The grouping suggests a simple explanation of the “photon localization” recently observed by Casati et al. [1].     

Microwave ionization of highly excited hydrogen atoms

Within a 1-dimensional model we calculate quantum mechanically the probability to ionize a highly excited hydrogen atom by a monochromatic microwave field. Based on a detailed analysis of the ionization process we developed a computational scheme as well as a simple physical framework which are presented and discussed. Our calculations are in good agreement with the experimental results. We show that the experimentally measured ionization thresholds are due to a sharp transition between two localization regimes and that recently measured structures below the classical chaos border are due to unresolved clusters of Floquet pseudo crossings. We propose an experimental method by which one could measure the distance and distribution of crossing Floquet eigenvalues.     

Empirische Beziehungen zur Sauerstoffkoordination um Antimon(III) und Tellur(IV) in Antimoniten und Telluriten

The strong variability of bond length between Sb(III) or Te(IV) and oxygen is correlated with distances to more distant oxygen atoms in the trans position. Closer approach of the trans-oxygen atom leads to lengthening of the bond in question. Hyperbolic functions represent suitable approximations for the correlations and give the bond lengths on the average within 0.04 Å. The distance relations are discussed for various limiting coordinations corresponding to 3, 4, and 5.     

Zur Polymorphie von SrTeO3

Beside the transition into a ferroelectric phase at 583 K, monoclinic SrTeO₃(I) at ?1260 K transforms slowly into a high-temperature form (SrTeO₃(II)) which after quenching undergoes rapid phase transitions at 648 and 733 K. X-Ray data of triclinic α-SrTeO₃(II) (room temperature), monoclinic β-SrTeO₃(II) (660 K), and monoclinic γ-SrTeO₃(II) (770 K) are presented.