Laser beacon wave-front sensing without focal anisoplanatism

Wave-front sensing from artificial beacons is normally performed by formation of a focused spot in the atmosphere and sensing of the wave-front distortions produced during the beam's return passage. We propose an alternative method that senses the distortions produced during the outgoing path by forming an intensity pattern in the atmosphere that is then viewed from the ground. A key advantage of this method is that a parallel beam is used, and therefore the wave-front measurements will not suffer from the effects of focal anisoplanatism. We also envisage other geometries, all based on the concept of projecting a pupil pattern onto the atmosphere.     

The Boolean algebra of the theory of linear orders

We characterize the isomorphism type of the Boolean algebra of sentences of the theory of linear orders. It is isomorphic to the sentence algebras of the theory of equivalence relations, the theory of permutations and the theory of well-orderings. This work was partially supported by the National Science Foundation under research grant MCS 76-07249.     

Algorithms for the calculation of the population distribution of species among energy levels in optically-thin systems

A model is presented which is suitable for rapid calculation of the population distribution among energy levels in systems which undergo collisional and radiative processes. To facilitate these calculations, algorithms have been derived which can be used over a wide range of conditions.     

Method for the rapid synthesis of highly functionalized 2-hydroxy-1-naphthoates. Syntheses of the naphthoic acid components of neocarzinostatin chromophore and N1999A2

We describe a four-step sequence for the synthesis of complex 2-hydroxy-1-naphthoic acids involving Z-selective olefination of benzaldehyde derivatives with a novel dioxolenone-containing phenyl phosphonate reagent, followed by dioxolenone cleavage with alkaline trifluoroethanol and oxidative cyclization (Mn(OAc)(3)) of the resultant trifluoroethyl beta-keto esters. [reaction: see text]     

Robust quantum communication using a polarization-entangled photon pair

Noise and imperfection of realistic devices are major obstacles for implementing quantum cryptography. In particular, birefringence in optical fibers leads to decoherence of qubits encoded in photon polarization. We show how to overcome this problem by doing single qubit quantum communication without a shared spatial reference frame and precise timing. Quantum information will be encoded in pairs of photons using tag operations, which corresponds to the time delay of one of the polarization modes. This method is robust against the phase instability of the interferometers despite the use of time bins. Moreover synchronized clocks are not required in the ideal no photon loss case as they are necessary only to label the different encoded qubits.     

True molar surface energy and alignment of surface molecules

By use of data for surface tension, for the first time a method is presented for calculating true molar surface properties of liquids: free energy, entropy, and enthalpy. These new data allow full comparison with other molar quantities, such as enthalpy and entropy of vaporization. All data are at the normal boiling point. There are differences in behavior between various classes of nonpolar compounds. Rare gases and tetrahydrides of Group 14 form a separate category. The results agree with the experimental findings that water and alcohol molecules are aligned with the -OH groups attached to the surface. The data indicate that hydrogen peroxide and 1,2-ethanediol also have one -OH group directed toward the surface and one directed out toward the vapor phase. Small straight-chain amines have some structure at the surface, but the larger ones behave like the corresponding alkanes. Very polar compounds, such as nitriles, nitro compounds, and aldehydes, have little or no increased degree of order of molecules at the surface. Except for hydrogen-bonded compounds, molecules at the surface have surroundings similar to those in the bulk liquid.     

High average power,all-solid-state external resonator Raman laser

As much as 3 W of average power at 1064 nm from a diode-pumped Nd:YAG laser, Q switched at 4 kHz, was used to pump an external-resonator, crystalline Ba(NO3)2 Raman laser generating a maximum of 1.3-W output at the first Stokes wavelength of 1197 nm. The slope efficiency was 63% with respect to the fundamental power incident on the Ba(NO3)2 crystal. A reduction in the beam quality of the Stokes output from M2 approximately 1.4 at lower Stokes powers to M2 approximately 3.4 at higher powers is attributed to thermal loading of the Raman-active crystal.