Strongly self-complementary and hereditarily isomorphic tournaments

A tournament is strongly self-complementary if every subtournament is self-complementary. TournamentsR, B defined on the same vertex setV are hereditarily isomorphic if for every subsetA ofV, the induced subtournamentsR(A) andB(A) are isomorphic. We determine all strongly self-complementary tournaments and apply this result to characterize the paris of hereditarily isomorphic tournaments.     

Exact solution to a nonlinear Klein-Gordon equation

The nonlinear Klein-Gordon equation ?^μ?_μΦ + M²Φ + λ₁Φ^1?m + λ₂Φ^1?2m = 0 has the exact formal solution Φ = [u^2m ?λ₁u^m/(m ? 2)M²+λ₁²/(m?2)²M⁴?λ₂/4(m ? 1)M²]^1/mu^?1, m ≠ 0, 1, 2, where u and v^?1 are solutions of the linear Klein-Gordon equation. This equation is a simple generalization of the ordinary second order differential equation satisfied by the homogeneous function y = [au^m + b(uv)^m/2 + cv^m]^k/m, where u and v are linearly independent solutions of y″ + r(x) y′ + q(x) y = 0.     

Dynamics of the optically pumped midinfrared NH3laser at high pump power--Part II: Raman gain and ac stark shifts

Coherent effects produced by high-intensity pumping onaR(6, 0) in NH3are investigated for both the pure gas and for mixtures with an inert buffer gas. Two different Raman transitions are observed. One is the usual directly pumped Raman transition, and the other is pumped indirectly since it first requires a large population transfer to the upper vibrational level. This population transfer also creates inversion gain, shifted away from line center due to ac Stark shifts, on both transitions. Raman gain coefficients of 10 percent ċ cm^-1and inversion gain coefficients > 2 percent ċ cm^-1are observed, and compared to a combined density-matrix and rate-equation model.     

The long range part of the parity-violating electron form factor in the Weinberg-Salam model

The long-range part of the parity-violating electron muon interaction is calculated in fourth order in the Weinberg-Salam model. Independent of the non-abelian gauge, a range of about 50fm is found. Possible applications are suggested.     

Fabrication and characterisation of long-wavelength, GaInAs/AlGaInAs/InP modified-MQW lasers

Room-temperature operation of GaInAs/AlGaInAs/InP M-MQW lasers grown by low-pressure MOVPE is described for the first time. Threshold current densities were as low as 1.9 kA cm/sup -2/ with emission wavelengths of 1.59 mu m.<>     

Quantum statistics of degenerate four wave mixing

A microscopic model of degenerate four wave mixing including the quantisation of the atomic medium is analysed. In the limits of large detuning, low saturation and zero loss, ideal squeezing in the output field is possible. The effect of nonoptimal conditions is analysed.     

New techniques for determining vibrational temperatures, dissociation, and gain limitations in CW CO2lasers

We have developed an accurate method of determining vibrational temperatures and populations in CO2laser discharges. Our technique involves the use of both the regular 00 ° 1 and sequence 00 ° 2 laser transitions as probes of a CO2laser amplifier. We have been able to separately investigate the quantitative effects of gas heating, dissociation, and ν3mode excitation efficiency on the small-signal gain in typical CW CO2lasers. In general we find that the maximum gain attained in a typical flowing gas CW CO2laser is limited by dissociation of CO2at high discharge currents. To investigate the more fundamental limitations on the gain, we used a short discharge tube with fast flow rates. Contrary to many previous results, we find that thermal effects play a somewhat secondary role in the discharge dynamics, and that the lower laser level populations are small under all discharge conditions. Our results show that the chief limitation on gain in CW CO2lasers is the "saturation" of the ν3mode vibrational temperature T3at high discharge currents. This saturation effect is observed for a wide range of gas mixtures and pressures, and has been studied in detail. Gain coefficients as high as 3.3 percent/cm have been obtained in a conventional 1-cm bore CW discharge tube. We also report preliminary results of an experiment which uses a tunable diode laser to measure gain on a large variety of transitions in a CO2discharge. The diode laser measurements give a striking confirmation of the results described above, and provide the first direct experimental evidence that a Boltzmann distribution exists in the vibrational modes of discharge excited CO2.