Physics going soft: The emergence of soft condensed matter physics

The recent development of intense, ultrashort, table top lasers in the mid-infrared opens new avenues for research in strong field atomic physics. Electrons submitted to such radiation acquire huge quiver energies, even at moderate intensity and interesting properties arise: first, the wavelength offers a convenient experimental knob to tune the ionisation regime by controlling the Keldysh parameter. Second, many processes like above-threshold ionisation or high harmonic generation, whose characteristics depend directly on this energy, can be pushed to unprecedented limits. Third, the wavelength controls the spectral phase of the harmonics and hence the possibility to improve the generation of pulses in the attosecond regime. Recent studies of rare gas and alkali atoms' photoelectron spectra and harmonic generation at 2 and 3.6 μm have begun to confirm the theoretical predictions. However, unexpected features have also been found showing that strong field interaction still keeps some secrets after more than 40 years of investigation.     

Formation of self-supporting reversible cellular networks in suspensions of colloids and liquid crystals

In mixtures of thermotropic liquid crystals with spherical poly (methyl methacrylate) particles, self-supporting networklike structures are formed during slow cooling past the isotropic-to-nematic phase transformation. To characterize the process of network formation in terms of morphology, phase transformation kinetics, and mechanical properties, we have combined data from polarization and laser scanning confocal microscopy with calorimetric, NMR, and rheological results. Our data suggest that the mechanism of network formation is dominated by a broadened temperature and time interval of phase transformation rather than by particle size or concentration. The observation that the width of the transformation interval strongly depends on sample preparation supports the hypothesis that a third component, most likely alkane remnants slowly liberated from the particles, plays a crucial role. In addition, calorimetric findings for liquid crystal/colloid mixtures, heated and cooled up to 13 times, point to separation of the liquid crystal into two compartments with different phase transformation kinetics. This could be explained by redistribution and enrichment of alkane in the particle-composed network walls. A further increase of the storage modulus, G', and incomplete dissolution of the networks in the isotropic state indicate that the formation of two compartments during repeated temperature cycles stabilizes the network and confers strong memory effects.     

Layer spacings in coherently strained epitaxial metal films

Laterally resolved measurements of the quantum size effect (QSE) in electron reflectivity are made with low energy electron microscopy on coherently strained Ag films on a W(110) surface. The evolution of the total film thickness with increasing number of atomic layers is determined accurately by dynamical theory analysis of the QSE features. Combined with a model of layer spacings obtained from first-principles calculations, this provides for a novel approach to determine the buried interface layer spacing, which is inaccessible to other methods.     

Measurement of neutrino oscillation with KamLAND: evidence of spectral distortion

We present results of a study of neutrino oscillation based on a 766 ton/year exposure of KamLAND to reactor antineutrinos. We observe 258 nu (e) candidate events with energies above 3.4 MeV compared to 365.2+/-23.7 events expected in the absence of neutrino oscillation. Accounting for 17.8+/-7.3 expected background events, the statistical significance for reactor nu (e) disappearance is 99.998%. The observed energy spectrum disagrees with the expected spectral shape in the absence of neutrino oscillation at 99.6% significance and prefers the distortion expected from nu (e) oscillation effects. A two-neutrino oscillation analysis of the KamLAND data gives Deltam(2)=7.9(+0.6)(-0.5)x10(-5) eV(2). A global analysis of data from KamLAND and solar-neutrino experiments yields Deltam(2)=7.9(+0.6)(-0.5)x10(-5) eV(2) and tan((2)theta=0.40(+0.10)(-0.07), the most precise determination to date.     

Experimental demonstration of waveguide-coupled round-cornered octagonal microresonators in silicon nitride

We report laterally waveguide-coupled octagonal microresonators with designed round resonator corners in silicon nitride. We demonstrate nearly single-mode add-drop filter characteristics, when 50-microm-size round-cornered octagonal microresonators are used, with an optimum coupling efficiency exceeding 96%, a finesse of approximately 30, and a Q of approximately 6400. Our experiments also reveal two unforeseen phenomena in certain microresonator shapes: a pronounced drop in coupling efficiency and resonance notches in the drop spectrum. These device characteristics hint at the recently postulated multiple orbit interference in waveguide-coupled polygonal microresonators.     

Stereoselective photooxidation of enecarbamates: reactivity of ozone vs singlet oxygen

[reaction: see text]. Oxazolidinone-functionalized enecarbamates show contrasting behavior upon oxidation by singlet oxygen and by ozone. The observed stereoselectivity difference indicates that the oxidation with ozone is subject to classic steric effects, whereas the very high selectivity in the photooxidation with singlet oxygen is derived from vibrational deactivation.     

Projective embeddings of complex supermanifolds

We generalize the Kodaira Embedding Theorem and Chow's Theorem to the context of families of complex supermanifolds. In particular, we show that every family of super Riemann surfaces is a family of projective superalgebraic varieties.Research supported in part by NSF grant DMS-8704401Research supported in part by NSF grant DMS-4253943Research also supported in part by NSF grant DMS-4253943     

Algebraic recurrence relations for the finite-order scattering and transmission functions

In preceding papers (cf. Bellmanet al.(^1,2,3,), integral recurrence for the finite-order scattering and transmission functions have been given in connection with integral recurrence relations for the finite order X- and Y-functions with the aid of an initial-value method. In the present paper, it is shown how to find algebraic recurrence relations for the finite-order scattering and transmission functions in terms of finite-order X- and Y-functions without referring to an initial-value method. These recurrence relations are suitable for the numerical computation of the finite-order scattering and transmission functions by use of a digital computer. Furthermore, in Tables 1–3, a numerical example of the finite-order reflection functions for optical thickness 0·2 with albedo = 1 is listed. Table 4 furnishes an example of the cumulative reflection functions for optical thickness 0·2 with three different albedos.     

Microwave absorption of oxygen measured with a Fabry-Perot spectrometer

A Fabry-Perot interferometer in the semiconfocal configuration has been used as a microwave spectrometer by the method of Q-reduction. The Q can be determined with conventional laboratory equipment to within 2% accuracy, corresponding to 0.3 dB/km at 58.82 GHz. Absolute of pure oxygen and dry air at fixed frequencies has been measured as a function of pressure from 0 to 1 atm at room temperature. The measured absorption of dry air can be explained if the overlap of the oxygen lines is properly taken into account.     

Numerical results for finite order X and Y functions of radiative transfer

It is well known that, in the theory of radiative transfer, Chandrasekhar's X and Y functions play an important role in the diffuse reflection and transmission problem (cf. Chandrashekhar⁽¹⁾). In a preceding paper (cf. Bellmanet al.⁽¹⁰⁾), graphs and selected tables of these functions covering wide ranges of slab thickness and albedos for single scattering have been provided. In this paper, making use of a system of coupled integral recurrence relations for finite order X and Y functions (cf. Bellmanet al.⁽¹⁴⁾), numerical results for these basic functions are tabulated up to optical thickness τ = 2.0 from τ = 0.1, assuming the conservative case of isotropic scattering. The maximum order of these functions is taken to be fifteenth. It is shown that the accuracy obtained is satisfactory in the domain under consideration. Furthermore, numerical results for Chandrasekhar's approximation for X and Y functions are also tabulated for stabs of small optical thickness.