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  • 1.
    Bustad, Johnny
    Högskolan i Gävle, Institutionen för matematik, natur- och datavetenskap. Natur.
    Computational studies of core level XPS satellites in transition metal systems: Department of Quantum Chemistry, Uppsala University1995Doktorsavhandling, monografi (Övrigt vetenskapligt)
    Abstract [en]

    Upon core ionization of a free molecule or a molecule adsorbed on a metal surface, higher binding energy satellites are observed, so called "shake-up" satellites, which can be viewed as valence excitations simultaneously to the creation of the core hole. In this thesis, theoretical studies of such core level XPS satellites in transition metal systems are presented, as well as cluster calculations of XES spectra, using the quantum mechanical INDO method. The main motivation of these studies is to get a more detailed understanding of the bonding between the adsorbed molecules and the metal and the screening process accompanying the creation of the core hole. This interest is motivated by fundamental questions about the adsorbate-substrate interaction as well as technical applications, such as catalysis.

    It has been found that many aspects of extended adsorbate systems, where CO is coordinated to metal atoms, can be modelled by transition metal carbonyls such as Mo(CO)6, Cr(CO)6 and Ni(CO)4. The bonding between the core ionized CO group and the transition metal, consists of an interaction between, on the one hand, the sigma lone pair of the ligand and, on the other hand, the metal d-orbitals and the CO antibonding pi-star orbital of the CO-group, i.e. a sigma donation from the ligand and pi donation from the metal. It is the changes in this bonding which are responsible for the dominant features of the shake-up spectra in the studied model molecules. The main conclusion of the three abovementioned case studies is that new excitations involving charge transfer from the metal to the ionized ligand occur with significant probability in the metal carbonyls, in addition to the internal excitations present also in free CO.

    In extending the model towards larger systems, calculations of CO/Ni(100), N2//Ni(100), CO/Cu(100) and benzene/Cu(100) were undertaken, where the metal surface was modelled by clusters of 1-12 metal atoms. Many of the features from the metal carbonyls are found also in these systems. The most important added feature is the presence of high-intensity metal-metal excitations, which mainly affect the shape of the main line.

    Ground state cluster calculations were performed to explain the XES spectra of CO adsorbed on Ni(100) and Cu(100) surfaces. It was found that the calculations reproduce the important characteristics of the experimental spectra, and were used as a support for the assignments of the involved states.

  • 2. Chen, R.
    et al.
    Wang, M.
    Wang, S.
    Liang, Hao
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för elektronik, matematik och naturvetenskap, Elektronik.
    Hu, X.
    Sun, X.
    Zhu, J.
    Ma, L.
    Jiang, M.
    Hu, J.
    Li, J.
    A low cost surface plasmon resonance biosensor using a laser line generator2015Ingår i: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 349, s. 83-88Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Due to the instrument designed by using a common surface plasmon resonance biosensor is extremely expensive, we established a portable and cost-effective surface plasmon resonance biosensing system. It is mainly composed of laser line generator, P-polarizer, customized prism, microfluidic cell, and line Charge Coupled Device (CCD) array. Microprocessor PIC24FJ128GA006 with embedded A/D converter, communication interface circuit and photoelectric signal amplifier circuit are used to obtain the weak signals from the biosensing system. Moreover, the line CCD module is checked and optimized on the number of pixels, pixels dimension, output amplifier and the timing diagram. The micro-flow cell is made of stainless steel with a high thermal conductivity, and the microprocessor based Proportional-Integral-Derivative (PID) temperature-controlled algorithm was designed to keep the constant temperature (25 °C) of the sample solutions. Correspondingly, the data algorithms designed especially to this biosensing system including amplitude-limiting filtering algorithm, data normalization and curve plotting were programmed efficiently. To validate the performance of the biosensor, ethanol solution samples at the concentrations of 5%, 7.5%, 10%, 12.5% and 15% in volumetric fractions were used, respectively. The fitting equation ΔRU=-752987.265+570237.348×RI with the R-Square of 0.97344 was established by delta response units (ΔRUs) to refractive indexes (RI). The maximum relative standard deviation (RSD) of 4.8% was obtained. 

  • 3.
    Wang, Zhao
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Miljöteknik.
    Liu, Longcheng
    Department of Chemical Engineering and Technology, Royal Institute of Technology, Stockholm, Sweden.
    Neretnieks, Ivars
    Department of Chemical Engineering and Technology, Royal Institute of Technology, Stockholm, Sweden.
    Hard-sphere fluid mediated interaction: a pressure expression with application of the weighted correlation approach2016Ingår i: Molecular Physics, ISSN 0026-8976, E-ISSN 1362-3028, Vol. 114, nr 5, s. 599-607Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    By using a so-called differential-integral method on the chemical potential of a hard-sphere fluid, a special variant of our previously developed expression that describes the interaction between charged plates immersed in an electrolyte, is introduced to examine the hard-sphere fluid mediated pressure in a slit. The resulting expression consists of a kinetic contribution and a hard-sphere contribution, and it is formulated as a function of the single-particle direct correlation function and the density distribution of a hard-sphere fluid. It allows us to conveniently apply the classic density functional theory to explicitly investigate the influence of the hard-sphere excluded-volume effect on the interaction pressure between surfaces. In this study, a newly proposed weighted correlation approach (WCA)-Denton and Ashcroft (DA) method is employed to predict the interaction pressure as well as its pressure components for a hard-sphere fluid inside a slit pore. Comparisons with the results from the Monte Carlo simulations and the fundamental measure theory suggest that the WCA-DA method is able to accurately capture the detailed characteristic pattern of the pressure-separation curves at different fluid densities. It is also found, both qualitatively and quantitatively, that the hard-sphere pressure contribution dominates over the kinetic pressure contribution in determining the oscillatory behaviour of the interaction pressure curves, especially when a hard-sphere fluid of high density is concerned.

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