Manipulation of photon statistics of highly degenerate incoherent radiation

Highly degenerate incoherent radiation has a Gaussian density matrix and a large occupation number of modes f. If it is passed through a weakly transmitting barrier, its counting statistics is close to Poissonian. We show that a second identical barrier, in series with the first, drastically modifies the statistics. The variance of the photocount is increased above the mean by a factor f times a numerical coefficient. The photocount distribution reaches a limiting form with a Gaussian body and highly asymmetric tails. These are general consequences of the combination of weak transmission and multiple scattering.     

Experimental investigation of the nonequilibrium velocity distribution function in a heat conducting gas

Preliminary measurements of the nonequilibrium velocity distribution function in a heat conducting gas have been carried out using a Doppler broadened absorption line. The experimental technique, which uses the coincidence of a Stark tunable line of NH₂D and the CO₂ P(20) laser frequency, is described. For molecular velocities that are not too high, the results are in good agreement with the Chapman-Enskog solution of the Boltzmann equation.     

A comparison of data on the viscomagnetic effect, flow birefringence and depolarized Rayleigh line broadening

A comparison of data on the viscomagnetic effect, flow birefringence and depolarized Rayleigh line broadening for various gases of linear molecules at temperatures between 90 and 293 K is carried out. From the combined results information is obtained on the scalar structure of the non-equilibrium angular momentum polarization produced in viscous flow.     

Kinetic theory of field effects in nonuniform molecular gases

Effects of magnetic and electric fields on transport phenomena in dilute polyatomic gases are reviewed within the framework of first order Enskog theory. The established technique of approximate operator inversion is used to give first order approximations of the transport coefficients. Instead of the customary expansion of polarization into orthogonal polynomials a more general treatment is chosen here so as to accomodate recent experimental observations. The polarizations produced by macroscopic fluxes are assumed to be eigenfunctions of the collision operator within the subspace of functions anisotropic in angular momentum. The formalism is extended to mixtures in a way to let the final expressions assume the same form as for pure gases. The obtained transport coefficients obey several symmetry relations and inequalities. Additional inequalities are now also derived for the matrix describing the saturated field effects.     

Flow birefringence in gases: The temperature dependence

A method is described for measurements of the temperature dependence of flow birefringence in gases between 90 and 293 K. Results are presented for CO, N₂, HD and oD₂.     

The Senftleben-Beenakker effect in ammonia and its mixtures with noble gases

Experimental results are presented for the influence of a magnetic field on the viscosity of NH₃-He and NH₃-Ar and on the thermal conductivity of NH₃-Ar gas mixtures. Data are reported for various mixture compositions at room temperature. The data are analyzed in detail in an attempt to clarify the unique behavior of ammonia.     

1B2u1A1g fluorescence from benzene produced by electron impact (30–1000 eV)

The ¹B_2u → ¹A_1g fluorescence resulting from electron impact (30–1000 eV) on benzene has been studied in the pressure range 10^?4 ?2 × 10^?3 torr. The fluorescence spectrum is compared with the spectrum obtained by other methods. The energy dependence of the absolute emission cross section indicates a small probability for internal conversion from higher singlet states to the ¹B_2u state.