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Notes: We have performed a detailed study of the helium/Si(111)–(1×1)H interaction, using a thorough set of experimental measurements combined with a first principles theoretical approach. An empirical potential is presented, which describes both diffraction from the repulsive part and selective adsorption resonances resulting from the helium–surface potential well. The 80 meV potential energy contour has a corrugation of 0.6 Å along the [1¯10] direction, and the well depth is 7.5 meV. The study is completed by a calculation of the helium/Si(111)–(1×1)H potential, based on the surface electron density using effective medium models. Comparison with the empirical potential provides insight into the nature of the helium–semiconductor interaction. © 2000 American Institute of Physics.

Notes: The present study examined whether employees high in negative affectivity (NA) are destined to be unhappy at work. Managerial employees provided information regarding perceptions of job characteristics, negative affectivity (NA), job satisfaction, and intentions to turnover. Using hierarchical regression, our findings suggest that employees who reported being high NA were more reactive to the environmental cues of perceived job scope. Specifically, NA interacted with job scope such that individuals high in NA who perceived their jobs as being higher (lower) in scope reported more (less) job satisfaction than did individuals low in NA. Implications for organizations and future research directions are discussed.

Notes: Calculations of focal properties and third-order aberration coefficients are presented for atom mirrors based on elastically deformed single-crystal surfaces. Biaxial loading of the mirrors is achieved by a combination of a uniform applied pressure and rectangular boundary conditions. The results are calculated for readily available single-crystal wafers of Si(111) with a thickness of 50 μm and a usable free standing diameter of 18 mm. Focusing of beams at non-normal incidence requires the principal radii of curvature, in planes normal to the mirror plane, to be different. The ratio of these principal radii of curvature is shown to be insensitive to the applied pressure and can be varied by a factor greater than 10 by changing the boundary conditions from square (1:1) to rectangular (1:2). © 1999 American Institute of Physics.

Notes: Focusing characteristics of asymmetrically bent single crystal mirrors are discussed in the context of fabricating an optic element for an helium atom microscope. We demonstrate the principle that deforming a clamped, elliptical, single crystal under electrostatic pressure can produce submicron focusing of an helium beam. We present a systematic procedure that may be used to fabricate high precision mirrors close to the Cartesian ideal of any chosen optical configuration. In particular, imaging systems with asymmetric mirror profiles are discussed. Results are independent of crystal characteristics and can be adapted to fit a range of experimental geometries. The calculations indicate that mirror-induced aberrations can be eliminated to fourth order by use of a single actuation electrode in an ideal system. © 2000 American Institute of Physics.

Notes: Two different definitions of phase shifts and time delays are contrasted and shown to match different experimental methods of generating delayed pulses. Phase shifts and time delays are usually defined in terms of a carrier wave in magnetic resonance, but definitions based on the envelope of a single pulse are useful in optics. It is demonstrated experimentally that a frequency domain measurement using spectral interferometry can simultaneously measure phase shifts with an accuracy of 0.1 rad (2σ) and time delays with a precision of 40 attoseconds (2σ) for 25 femtosecond optical pulses. Envelope time delays are generated by pathlength differences in an interferometer. Constant spectral phase shifts are demonstrated by diffracting pulses from a variable phase volume diffraction grating. Experimental requirements for phase-resolved spectroscopy are outlined. The theory of phase-locked pulse pair techniques is reexamined, and it is concluded that linear experiments with phase-locked pulse pairs are completely equivalent to Fourier transform absorption spectroscopy and do not measure the refractive index or real part of the susceptibility. It is shown that Fourier sine and cosine transformations of truncated time domain signals which do not match the symmetry of the complete signal can produce a false dispersive susceptibility because they are equivalent to Kramers–Kronig inversion of finite bandwidth absorption data. A procedure for shifting π/2 phase-locked transients by a quarter cycle of delay to generate a transient with a π/2 spectral phase shift is given. Equations used to calculate femtosecond nonlinear optical signals have assumed carrier wave delays. Modifications to these equations are required when envelope delays are generated by interferometer pathlength differences and modified equations are given. The modified equations yield significantly different results for phase-resolved or interferometric experiments. In particular, the modified equations are needed to calculate indirectly (interferometrically) detected frequencies and the real and imaginary parts of two-dimensional Fourier transform spectra. The role of the refractive index and real part of the frequency domain susceptibility in nonlinear experiments with phase-locked pulse pairs is explored. It is concluded that experiments such as the heterodyne detected stimulated photon echo are insensitive to nonlinear refractive index changes under some circumstances. Finally, modifications of some equations used in the theory of coherent control are needed to match theory with experimental practice. © 1999 American Institute of Physics.

Notes: The authors identify and define the end user computing (EUC) construct and operationalize the construct through development of a valid, reliable measure called the EUC activities scale. This scale is designed to distinguish specific, discrete computer activities performed on the job. The research analyzes the validity and reliability of the instrument based on data obtained from 776 university employees who participated in the initial, exploratory application. Exploratory factor analysis of the scale resulted in five factors. In order of increasing complexity of job-related computer activities, these factors are: beginning EUC activities, intermediate EUC activities, advanced EUC activities, EUC facilitation activities, and EUC infrastructure activities. The factor analysis, reliabilities, and known-groups analysis provide support for the construct validity of the instrument when used in a university setting. Suggestions are provided for further use of the scale in business environments to increase generalizability, refine the instrument, and help establish a coherent theoretical basis for further research in EUC.