Iodine photodissociation laser system Perun II

A construction and exploitation of a medium size iodine photodissociation laser system Perun II is reported. This laser produced pulses of infrared light (=1.315m) up to 50 J in energy and 300 ps in duration. The diameter of the beam is 82 mm. The beam divergence is about 4×10^–4 rad. The laser beam can be focused in a focal spot of a power density exceeding 10¹⁴ W/cm². The resuls of measurements of basic plasma parameters on an Al foil target are also presented. A recent improvement of the system includes a conversion to the second harmonic by a DKDP crystal.Presented at bilateral international seminar of High Temperature Laser Plasma and High Gain Iodine Lasers held on 4 July 1991 in the Inst. of Physics, Czechosl. Acad. Sci., in Prague (organized by Division of Optics of the Inst. of Physics, Czechosl. Acad. Sci., and Physical Section (Plasma Division) of the Union of Czech Mathematicians and Physicists.     

Two singular integrals containing a partial wave of the two-body coulomb T-matrix

The operatorsT _C,l E+i0)[–G ₀(E+i0)]^1–i andT _C,l(E+i)G ₀[–iG ₀(E+i)]ⁱ acting on spaces of Hölder continuous, differentiable and analytic functions are investigated. The results of their action are expressed in terms of explicit singular factors and terms and Hölder (differentiable, analytic) functions. The most singular part of these operators is shown to be determined by a simple functional.     

Elastic constants of the alloys Cd1−x Zn x (x<0.3%) and their temperature dependence

The temperature dependence of elastic constants of Cd_1–x Zn _x alloys, havingx=0.021, 0·042 and 0·233 at.%, has been measured in the temperature range from 4·2 to 300 K by the pulse-echo-overlap ultrasonic method. The adiabatic compressibilities and the Debye temperatures have been calculated. All elastic constants with the exception ofc ₄₄ increase slightly with the growing concentration of Zn.The summary of this paper was presented on the 7^th Conference on Ultrasonic Methods in ilina, September 11^th–13^th, 1980.     

pH-dependent electrochemical behaviour of hydrophilic ampholytic membranes

Ampholytic membranes were synthesized by copolymerizing (2-hydroxyethyl)methacrylate as the hydrophilic component, methacrylic acid and (N,N-diethylaminoethyl)methacrylate as ionogenic components (both ionogenic monomers in amounts 2.5 mol% or 10 mol%), and ethylenedimethacrylate as the crosslinking agent (3,5 or 10 mol%). The effects of pH on the swelling and membrane potentials of the membranes were investigated. The dependence of the membrane potentials on pH is characterized by the position of the isoelectric point and by the slope of the straight part of the dependence. This slope reflects the attained degree of ideality of the membrane. By varying the degree of cross linking and the content of ionogenic components, it is possible to vary the pH-dependent response of the membranes.     

Highly regioselective construction of spirocycles via phosphine-catalyzed [3 + 2]-cycloaddition

A direct entry to spirocycles with low to moderate regioselectivity was achieved by triphenylphosphine-catalyzed [3 + 2]-cycloaddition of active exo-methylenecycles (1) and ethyl 2,3-butadienoate (2). The regioselectivity of the reaction was greatly improved by using the bulky tert-butyl ester of the 2,3-butadienoate (5). The regioselectivity of the reaction was further enhanced by using the tert-butyl 2-butynoate as the substrate. This protocol provided an efficient entry to the skeleton of spirocarbocycles, especially spiro[4.n]alkanes.     

Analytic expressions for the partial waves of the off-shell two body coulomb T-matrix

Closed form expressions for all partial waves of the pure Coulomb off-shell T-matrix p¦ T_c,l.(k ²) ¦p are obtained. All singularities appear through simple special functions, which makes it possible to study the analytic properties of p¦ T_c,l(k²) ¦p as a function not only of one of the momentap, p but even of both of them. With use of the renormalization procedure found by Zorbas the transition to half-and on-shell values is performed reproducing known expressions. By the same method simple expressions for the partial waves of the Coulomb wave function in the momentum representation are found.     

Highest-weight representations ofsl(2, ℂ) andsl(3, ℂ) via canonical realizations

The infinite-dimensional representations of thesl(n+1, ) Lie algebras (maximal representations) constructed in our previous paper are studied on the two simplest examplesn = 1,2. The sufficient condition for irreducibility of the maximal representations is proved to be also necessary in these cases. It is further shown, that our method allows us to construct other set of infinite-dimensional highest-weight representations ofsl(3, ), so calledmixed representations which are irreducible in some cases when the maximal as well as the standard highest-weight representations (Verma modules) are reducible.Dedicated to the 25th anniversary of the Joint Institute for Nuclear Research.The authors are grateful to Prof. A. A. Kirillov, Dr. A. U. Klimyk, Dr. W. Lassner and Prof. D. P. Zhelobenko for stimulating discussions.     

Transient absorption and laser output of YAG : Nd

YAG : Nd grown under 98% Ar 2% H₂ protective atmosphere free of nitrogen or hydrocarbons showed after UV irradiation broad absorption peaked at 1·9×10⁴ cm^–1 which disappeared relatively slowly at room temperature. It was more intensive in oxygen treated samples than in those annealed in hydrogsn. Transient absorption suppresses laser output by the increase of absorption at 0·94×10⁴ cm^–1 (1064 nm) and, particularly in CW mode, by the anomalous rod deformation. YAG : Nd containing Fe ions (2·10^–4 wt%) showed no transient absorption.