54 research outputs found
The Nuclear Response in Delta-Isobar Region in the (He,t) Reaction
The excitation of a -isobar in a finite nucleus in charge--exchange
(He,t) reaction is discussed in terms of a nuclear response function. The
medium effects modifying a - and a pion propagation were considered for
a finite size nucleus. The Glauber approach has been used for distortion of a
He and a triton in the initial and the final states. The effects
determining the peak positions and its width are discussed. Large displacement
width for the - h excitations and considerable contribution of
coherent pion production were found for the reaction on C.Comment: 29 pages including 8 figures, IU/NTC 92-3
A 750 mW, continuous-wave, solid-state laser source at 313 nm for cooling and manipulating trapped 9Be+ ions
We present a solid-state laser system that generates 750 mW of
continuous-wave single-frequency output at 313 nm. Sum-frequency generation
with fiber lasers at 1550 nm and 1051 nm produces up to 2 W at 626 nm. This
visible light is then converted to UV by cavity-enhanced second-harmonic
generation. The laser output can be tuned over a 495 GHz range, which includes
the 9Be+ laser cooling and repumping transitions. This is the first report of a
narrow-linewidth laser system with sufficient power to perform fault-tolerant
quantum-gate operations with trapped 9Be+ ions by use of stimulated Raman
transitions.Comment: 9 pages, 4 figure
Second harmonic generation and birefringence of some ternary pnictide semiconductors
A first-principles study of the birefringence and the frequency dependent
second harmonic generation (SHG) coefficients of the ternary pnictide
semiconductors with formula ABC (A = Zn, Cd; B = Si, Ge; C = As, P) with
the chalcopyrite structures was carried out. We show that a simple empirical
observation that a smaller value of the gap is correlated with larger value of
SHG is qualitatively true. However, simple inverse power scaling laws between
gaps and SHG were not found. Instead, the real value of the nonlinear response
is a result of a very delicate balance between different intraband and
interband terms.Comment: 13 pages, 12 figure
Calculation of SHG in periodically poled crystals by specifying a spatially periodic dependence of the quadratic nonlinearity in a single-domain crystal
A method is developed for calculating SHG in linearly homogeneous periodically poled nonlinear crystals (PPNC) by specifying a spatially inhomogeneous periodic distribution of the quadratic-nonlinearity parameter in the form of a 'small-scale' elliptic sine, whose half-period forms one domain with the characteristic 'microplateau' of the nonlinearity parameter and interdomain walls. It is found that, because the domain length should be equal to the coherence length when the quasi-phase-matching condition is fulfilled, and if the coherence length is calculated in the fixed-field approximation, the dependence of the harmonic amplitude on the longitudinal coordinate has the form of a 'large-scale' elliptic sine with a broad 'macroplateau' corresponding to a certain (in the case of quasi-phase matching, to virtually 100%) transformation; however, the mismatch in a domain is never completely compensated by the reciprocal lattice vector. In this case, the phase trajectories inside one domain have the form of a sequence: an unstable focus, a limit cycle ('macroplateau'), a stable focus. This picture repeats in the next domain. It is shown that the width of the SHG phase-matching curve in a PPNC in the regime of strong energy exchange, taking secondary maxima into account, can be considerably (by several times) larger than the width calculated in the fixed-field approximation
Efficiency of Passive Utilization of Ground âColdâ in Adaptive Geothermal Heat Pump Heating and Cooling Systems (AGHCS)
This article deals with estimating a potential and efficiency of utilization of passive ground âcoldâ for cooling buildings in climatic conditions of Moscow (Russia). The article presents results of numerical analysis to assess the efficiency of reducing peak cooling loads of the building equipped with AGHCS, through the utilization of natural cold of wells for passive cooling and cold storage in summer at night (off-peak) time with its subsequent consumption in the day time, both in passive mode, and with heat pumps. The conclusions of the article set out the basic principles of passive cooling in the design of AGHCS
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