Rotational spectroscopy and dynamics of carbonyl sulphide studied by terahertz free induction decays signals

A terahertz time domain spectroscopy experiment is used to study the coherent re-emission after exciting more than 60 energy rotational states of OCS molecules in gas phase. Due to the regular structure of the absorption spectrum of such linear molecules, a set of subsequent pulses separated by 82.6 ps is re-radiated from the vapour and recorded up to 450 ps. A model based on a linear response of the gas and by use of “Maxwell-Bloch” equations has permitted the re-emitted free induced decay to be investigated. Spectroscopic parameters, such as rotational constant, centrifugal distortion coefficient and relaxation times are responsible for the temporal shape and so can be evaluated. The influence of the optical thickness to access the relaxation times is discussed.     

Fission yields at different fission-product kinetic energies for thermal-neutron-induced fission of 239Pu

At the recoil spectrometer “Lohengrin” of the Institut Laue-Langevin in Grenoble, the yields of the light fission products from the thermal-neutron-induced fission of ²³⁹Pu were measured as a function of A, Z, the kinetic energy E and the ionic charge states q. The nuclear charge and mass distributions summed over all ionic charge states were determined for different light fissionproduct kinetic energies between 93 and 112 MeV. The proton odd-even effect which was measured to be (11.6 ± 0.6)% causes considerable fine structure in the yields. The average kinetic energy of even-Z elements in the light fission-product group is 0.3 ± 0.1 MeV larger than for odd-Z elements. The neutron odd-even effect is (6.5 ± 0.7)%. The comparison with previously published data ¹) for thermal-neutron-induced fission of ²³⁵U reveals a correlation between the proton odd-even effect in the yield and in the kinetic energy of the elements. The dependence of the proton odd-even effect on the fragmentation is very similar for ²³⁵U and ²³⁹Pu when it is considered as a function of the nuclear charge of the heavy fission products. The isobaric variances σ_z². for thermal-neutron fission of ²³⁵U and ²³⁹Pu coincide at all kinetic energies if the influence of the proton odd-even effect is averaged out. This supports the hypothesis that the magnitude of σ_z² is determined only by quantum-mechanical zero-point fluctuations. The influence of the spherical shells Z = 50 and N = 82 on the fragmentation is discussed.     

In-Situ Growth of Gadolinium Phthalocyaninato Sandwich Complexes on the Ag(111) Surface

We report a low-temperature scanning tunneling microscopy investigation of the in-situ growth of gadolinium phthalocyaninato complexes by combined deposition of free-base phthalocyanines and gadolinium atoms on a smooth Ag(111) substrate. A careful control of the stoichiometry allows the expression of a multilevel structurecomposed of irregularly distributed Gd_x-1(Pc)_x complexes, x=2–5, thus paving new avenues for surface-confined columnar growth.     

Theβ-decays of99Y and99Zr and the level schemes of99Zr and99Nb

Theβ-decays of⁹⁹Y and⁹⁹Zr have been investigated with the two recoil fission product separators JOSEF and LOHENGRIN. Half-lives of 1.51±0.08s and 2.1±0.1s respectively, have been determined. Aβ-decaying isomeric state has been observed in⁹⁹Y. The level schemes of ₄₀ ⁹⁹ Zr₅₉ and ₄₁ ⁹⁹ Nb₅₈ have been established fromγ-ray spectroscopy. Absoluteγ-intensities have been obtained by means of two independent techniques. Halflives of 293±10 ns for the 251.9 keV state and 10.2±1.5 ns for the 614.0 or 667.2 keV level in⁹⁹Zr have been measured through delayedβ,γ- andγ,γ-coincidence experiments. Values for the spins and parities of the low lying levels in⁹⁹Zr are proposed in accordance with the systematics of lighter odd Zr isotopes. Spins and partities are assigned to some levels in⁹⁹Nb fromγ,γ-angular correlation measurements. In this nucleus there is evidence for three-particle configurations of some excited states, where the odd proton is coupled to two neutrons which are in different orbits.     

Metal–organic interaction probed by First Principles STM simulations

The Review is devoted to recent progress made from the combination of Scanning Tunneling Microscope (STM) experiments and First Principles atomistic simulations in the chemical characterization of metal–organic interfaces. Density Functional Theory (DFT) has now reached the point to mimic in a quantitative way two pillars of the STM probe: the imaging mode convoluting the topographic and electronic properties and the spectroscopy modes comprising of elastic and inelastic detection ways. We present a selection of hybrid interfaces ranging from isolated benzene derivatives to thin honeycomb carbon film – a single graphene layer – deposited onto transition metal surfaces. The direct experimental analysis of these interfaces was error-prone, necessitating the confrontation with First Principles atomistic simulations. The few examples thus illustrate the power of different kinds of STM simulations to complement the STM data, in order to unambiguously identify the chemical structure of organic adsorbates.