GA/GV measured in the decay of polarized neutrons

A measurement of [G_A/G_V] in the decay of polarized neutrons, basically quite similar to our 1968 one, gives a value of 1.258±0.015. The asymmetry coefficient, A, is ?0.113±0.006. These results include the 1968 data.     

The ν2 + ν4 band of 12CF4

From a high-resolution diode laser spectrum of cooled ¹²CF₄, line assignments in ν₂ + ν₄ at 1066.4 cm^?1 have been made for tetrahedral subspecies to J = 20, and in many cases to higher J. Spectroscopic constants have been obtained from a least-squares fit of the Hamiltonian, and the relative intensities of the assigned lines have been calculated. The ground- and excited-state rotational constants, Coriolis constant, and splitting of the F₁ and F₂ vibrational substates have the values a.The CF bond length in the ground vibrational state is thus $\text{r}{}_0\text{= 1.31752 ± 0.00007}\text{A}\text{?}$. The analysis of a combination band such as this provides a method of obtaining ground-state spectroscopic constants of spherical-top molecules directly from the infrared spectrum, without the necessity of measuring weak “forbidden” transitions. The assignments allow accurate predictions of the frequencies emitted by the CO₂-pumped CF₄ laser.     

The perturbations of line frequencies in high-J manifolds of the ν3 band of SF6

In the diode laser spectra of several P- and R-branches of high-J manifolds in the ν₃ band of SF₆ it has been observed that the lines are shifted away from the positions predicted by the diagonal F_A1pp^(4,R,R) approximation of Moret-Bailly. The shifts form a smooth function of the line positions across each manifold; this function can be represented empirically by a parabola, to which the measured wavenumbers fit within experimental accuracy. This phenomenon is explained here by model calculations for P-, Q-, and R-branch excited state levels that perturb each other through higher-order vibration-rotation interactions. In the analysis, eigenvalues calculated by second-order perturbation theory are compared with those obtained by diagonalization of the Hamiltonian.     

The exponential interaction in Rn

We prove that the Schwinger functions for the ultraviolet cut-off exponential interaction with euclidean measure exp {;?λ∫Λ:e^αξk(x):dx} dμ₀(ξ/ ∫ exp{?λ∫Λ:e^αξk(x):dx} dμ₀(ξ), λ > 0, converge as the ultraviolet cut-off is removed. The limits are the free Schwinger functions in the case of space-time dimension n ? 3. In the case n = 2 this holds for |α| sufficiently big, whereas for |α| < 2 √π, one has the well-known nontrivial Schwinger functions of the exponential interaction.     

Rate coefficients and final states for the dissociative recombination of LiH+

The dissociative recombination of LiH+ ions with low-energy electrons is observed at a storage ring and the final states are analyzed using fragment imaging and field ionization techniques. The rate coefficient is found to be larger than its estimated value used in astrophysical models. Mostly the highest energetically possible Rydberg states of the lithium atom are populated by the reaction, indicating a common trend for molecular recombination via the noncrossing mode.     

CAN: an example of nonclassical acoustic nonlinearity in solids

A new class of nonlinear acoustic phenomena has been observed for acoustic wave interaction with simulated and realistic nonbonded contact interfaces (cracked defects) in solids. "Nonclassical" effects are due to substantially asymmetric stiffness characteristics of the interface for normal stress that results in specific contact acoustic nonlinearity (CAN). The asymmetry in the contact restoring forces causes the stiffness parametric modulation and instability of oscillations, which results in acoustic wave fractional subharmonic generation. The CAN subharmonics and higher harmonics reveal threshold dynamic behaviour, evident hysteresis, and instability effects.