Magnus expansion for rotationally induced inner-shell excitation

The exponential expansion (“Magnus expansion”) of the quantum-mechanical time-evolution matrix is applied to rotationally induced inner-shell excitation in atomic collisions. It is shown that this type of excitation process provides a particularly transparent case for studying the convergence properties of the Magnus expansion. Explicit results are presented for 2pπ-2pσ rotational coupling in Ne + Ne collisions.     

Variational method for inner-shell excitation in heavy-ion collisions

In the framework of the monopole model we study a perturbation method for inner-shell excitation which covers the whole projectile velocity region. This is achieved by introducing a velocity-dependent variational parameter and minimizing the time-dependent perturbation. We apply the method to theK-excitation of nonrelativistic systems.     

Non-perturbative study of rotationally induced inner-shell excitation

Within the time-dependent formulation of atomic scattering theory, the exponential representation (“Magnus expansion”) of the quantum mechanical time-evolution matrix is used in a non-perturbative study of rotationally induced inner-shell excitation in slow ion-atom collisions. The impact-parameter dependence of this type of process is shown to represent a transparent example for testing the convergence properties of the Magnus expansion. The specific structure of the Magnus expansion for multi-state rotational coupling in the vicinity of a united-atom (n, l) shell is investigated, and the analytic solution which this problem admits in the sudden limit is discussed. Explicit calculations within the Magnus approach have been performed for typical two-state and three-state problems relevant toK-shell andL-shell excitation. Their results are compared to the results of the sudden approximation and of coupled-state calculations. Good agreement between the Magnus results and the coupled-state calculations is obtained throughout if terms up to third order are retained in the commutator expansion of the exponent matrix associated with the time-evolution matrix.     

Heavy-ion excitation of 3− states in deformed nuclei

Previously measured data for 70.4 MeV ¹²C excitation of 3^? states in ^{148, 150}Nd are reanalyzed using a third-order rotational-vibrational model. Calculations using 3^? quadrupole moments which are expected if they are K = 0 states are in reasonable agreement with the magnitude of the large-angle data, but the quality of the fit in the Coulomb-nuclear interference region is only fair. It is found that the matrix element 〈2⁺∥M(E3)∥3^?〉 plays an important role in the calculations making the “measurement” of the 3^? quadrupole moments very difficult, if not impossible.     

Time-resolved luminescence of complex wide-gap oxide crystals under inner-shell excitation

In order to investigate the soft X-ray energy transformation in oxide detectors the optical spectra of several wide-gap oxide crystals were analyzed. The time-resolved luminescence (2.5–10.5 eV) and luminescence excitation spectra (50–200 and 500–630 eV) as well as decay kinetics of luminescence at 10 and 295 K were recorded using the synchrotron radiation from BW3 channel (HASYLAB, DESY). Several analogous features were discovered in the excitation spectra of both intrinsic self-trapped exciton luminescence and recombination luminescence for BeO, BeAl₂O₄, Be₂SiO₄ and AlPO₄ crystals under inner-shell excitation. Simultaneously, the excitation of Ce³⁺-luminescence in scintillating Be₂La₂O₅-Ce crystals significantly differs.     

Intrinsic luminescence in oriented BeO crystals under VUV and inner-shell excitation

Beryllium oxide (BeO) crystals were investigated by time-resolved low temperature VUV-spectroscopy at the SUPERLUMI station and BW3 beam line of HASYLAB (DESY, Hamburg). Photoluminescence spectra (3–10.5 eV), luminescence decay kinetics upon selective photoexcitation, as well as luminescence excitation (50–650 eV) and reflectivity (9–35 eV) spectra were measured and analyzed for oriented BeO crystals. It was shown that study of oriented crystals makes the traditional time-resolved spectroscopy method essentially more informative. Formation of the self-trapped exciton excited states of different multiplicity was found to sensitively depend on excitation energy and mutual orientation of the crystal's C optical axis and electric vector E of exciting polarized synchrotron radiation.     

Possible evidence for deconfinement in hadron collisions

The collision of hadrons at very high energies produces an entity whose energy density is extremely large resulting in the emission of a large number of hadrons. Though the entity may not have transited into the deconfined parton phase, the very high energy density may cause more than one charged hadron to be emitted at any instant. This yields a new multiplicity distribution, termed the GS distribution which fits the data as well as the popular negative binomial distribution. Neither the GS nor the NB distribution alone agrees with the data beyond 200 GeV, but a weighted sum of GS and NB distributions fits the experimental results exceedingly well. Since the negative binomial distribution arises from the branching of partons, we interpret the increase with energy of the negative binomial component in the weighted sum as the onset of a deconfined phase. The rising cross section for the negative binomial component parallels very closely the inclusive cross section for hadron jets which also is considered a consequence of parton branching.     

Possible evidence for the relaxation case in CdS

Possible evidence for the effects characteristic of the relaxation case (in which the dielectric relaxation time τ_d=ε? exceeds the minority carrier diffusion length life time τ₀) was observed by photoconductivity experiment in InCdSIn structure. A deviation from linearity in the relationship between conductivity (σ - σ₀) and light intensity (I) is consistent with an analysis based on the theory of relaxation case semiconductor.     

Energy-loss straggling for protons and helium ions

Energy-loss straggling for protons and helium ions at 50–500 keV per nucleon has been measured in molecular and atomic gases. It is found that composition of the target and charge-state fluctuations of the projectile play an important role in straggling.