Ultraviolet photoelectron spectroscopy of Nb − 4 to Nb − 200

Abstract. We present UV (hν = 6.42 eV) photoelectron spectra of niobium cluster anions Nb − n in the size range from n = 4 to n = 200. The spectra exhibit a variety of patterns, which can be related to the geometrical structures of the clusters. The charging energies of the larger clusters are in very good agreement with the metallic sphere model. Nevertheless a strong size dependence of the work function is observed, which underlines the special properties of this transition metal. PACS. 33.60.Cv Ultraviolet and vacuum ultraviolet photoelectron spectra -36.40.Cg Electronic and magnetic properties of clusters -73.22.-f Electronic structure of nanoscale materials

Is the Unitarity of the quark-mixing-CKM-matrix violated in neutron β\beta-decay?

We report on a new measurement of neutron $\beta$-decay asymmetry. From the result \linebreak $A_0$ = -0.1189(7), we derive the ratio of the axial vector to the vector coupling constant $\lambda$ = ${\it g_A/g_V}$ = -1.2739(19). When included in the world average for the neutron lifetime $\tau$ = 885.7(7)s, this gives the first element of the Cabibbo-Kobayashi-Maskawa (CKM) matrix $V_{ud}$. With this value and the Particle Data Group values for $V_{us}$ and $V_{ub}$, we find a deviation from the unitarity condition for the first row of the CKM matrix of $\Delta$ = 0.0083(28), which is 3.0 times the stated error

Polyaniline/palladium nanohybrids for moisture and hydrogen detection.

Palladium nanoparticles display fascinating electronic, optical and catalytic properties, thus they can be used for various applications such as sensor fabrication. Conducting polymers such as polyaniline have also been widely used in sensor technology due to its cost effectiveness, versatility, and ease of synthesis. In this research, attention was given to unify the exceptional properties of these two materials and construct palladium nanoparticle coated polyaniline films to detect hydrogen and moisture. Electrochemical polymerization of aniline was carried out on gold sputtered epoxy resin boards. Polyaniline film was generated across a gap of 0.2 mm created by a scratch made on the gold coating prior to electrochemical polymerization. A palladium nanoparticle dispersion was prepared using sonochemical reduction method and coated on to polyaniline film using drop-drying technique. Polyaniline only films were also fabricated for comparative analysis. Sensitivity of films towards humidity and hydrogen was evaluated using impedance spectroscopy in the presence of the respective species. According to the results, polyaniline films exhibited an impedance drop in the presence of humidity and the response was significantly improved once palladium nanoparticles were incorporated. Interestingly, polyaniline only films did not respond to hydrogen. Nevertheless, palladium nanoparticle coated polyaniline films exhibited remarkable response towards hydrogen

Ultraviolet photoelectron spectroscopy of Nb

We present UV ($h\nu = 6.42$ eV) photoelectron spectra of niobium cluster anions Nb$_n^-$ in the size range from n=4 to n=200. The spectra exhibit a variety of patterns, which can be related to the geometrical structures of the clusters. The charging energies of the larger clusters are in very good agreement with the metallic sphere model. Nevertheless a strong size dependence of the work function is observed, which underlines the special properties of this transition metal

Photoelectron spectra of Na

Cold, size selected sodium and copper cluster anions have been studied by photoelectron spectroscopy. The structure of the uppermost part of the s-band of the copper clusters turns out to be close to identical to the one observed in the density of states of sodium clusters of the same size. This result indicates that in the studied size range sodium and copper clusters adopt the same geometries, and that electron-lattice interaction is of comparable strength in both systems. The observed s-band level density scales almost perfectly with the bulk Fermi energies of the materials, which demonstrates that close to the threshold both systems follow the same electron dispersion relation

Ultraviolet photoelectron spectroscopy of Si

Using a new experimental setup we have measured UV (hν = 6.4 eV) photoelectron spectra of cold silicon cluster anions Si$_n^-$ in a very broad size range. For sizes up to n=46 the spectra exhibit rich structures. For larger sizes only smooth spectra have been obtained. No trace of a bandgap has been found even for clusters with more than 1000 atoms