Showing papers by "Andrey Popov published in 1997"

Evidence for exotic meson production in the reaction pi- p ---> eta pi- p at 18-GeV/c

Abstract: The {eta}{pi}{sup {minus}} system has been studied in the reaction {pi}{sup {minus}}p{r_arrow}{eta}{pi}{sup {minus}}p at 18 GeV/c. A large asymmetry in the angular distribution is observed indicating interference between L-even and L-odd partial waves. The a{sub 2}(1320) is observed in the J{sup PC}=2{sup ++} wave, as is a broad enhancement between 1.2 and 1.6 GeV/c{sup 2} in the 1{sup {minus}+} wave. The observed phase difference between these waves shows that there is phase motion in addition to that due to a{sub 2}(1320) decay. The data can be fitted by interference between the a{sub 2}(1320) and an exotic 1{sup {minus}+} resonance with M=(1370{plus_minus}16{sup +50}{sub {minus}30}) MeV/c{sup 2} and {Gamma}=(385{plus_minus}40 {sup +65}{sub {minus}105}) MeV/c{sup 2} . {copyright} {ital 1997} {ital The American Physical Society}

Observation of the two-photon photoelectric effect in low-intensity optical fields during photostimulated fractal aggregation of colloidal silver

Abstract: The two-photon photoelectric effect enhanced by the characteristic local fields of fractal nanostructures is observed in optical fields with intensity of the order of 10−3 W/cm2.

Resonant four-wave frequency mixing in Doppler-broadened transitions

Abstract: The influence of nonlinear interference processes and of changes in populations in strong electromagnetic fields, and also of the Doppler broadening on resonant four-wave frequency mixing is investigated for a system of Raman-type transitions. The case in which a quantum system interacts with one weak field and two strong fields is considered. Each of the energy levels is assumed to be perturbed by just one strong field. It is shown that the Doppler broadening alters drastically the contributions of the populations of the various levels to the investigated process and that this can alter by several orders of magnitude and nonlinear susceptibilities averaged over the velocities and influence significantly the selection of optimal configurations of the transitions and of the experimental conditions for effective resonant four-wave conversion of the radiation frequencies. A numerical analysis of the derived expressions is used to account for the experimentally observed considerable differences between the spectral dependences of the output power and the conclusions drawn from perturbation theory.

Dependence of the rate of photoinitiated formation of fractal aggregates in silver hydrosols on the wavelength of irradiating light

Abstract: The rates of photoinitiated growth of fractal structures in a typical silver hydrosol were studied experimentally at irradiating light wavelengths from 366 to 1050 nm. It was discovered that the process mentioned has a red threshold and that the process rate is minimal in a certain intermediate spectral region. A concept proposed to explain the results suggests that photoinitiated aggregation proceeds by a mechanism involving photoemission. The concept also accounts for the effect of local field amplification typical of the fractal media. The two-photon photoeffect was discovered for the first time in weak optical fields (the intensity of the order of 10 -3 W/cm 2 ). The photoeffect is enhanced by the effect of the local field. A principally new method of determining the degree of hydrosol aggregation is proposed.