Transverse Spatial Distribution Research Articles

Effect of the laser transverse spatial distribution on multiphoton ionization processes

In this paper, the dependence of the photoionization cross section σ2, total ion number Ni and the FWHM of photoionization spectral line in resonant multiphoton ionization processes (RMPI) upon the parameter C of the laser transverse spatial distribution has been studied. Considering the effects of spatial coordinate on the resonant multiphoton absorption cross section σ1, the limited dimension of the laser-molecular interaction volume and threshold of laser intensity for RMPI, we deduce the expression of σ2 vs the parameter C. We calculated the value of σ2 for (2+2)PI of benzene by numerical method, and compared the result with that obtained by Bruzzeste et al. In addition, we also present the total ion number of photoionization and the FWHM of photoionization spectral line as a function of the parameter C.

Center-of-mass energy distributions of the fragments from the collisional breakup reaction H3+-->H++H++H- in argon at high velocities.

We have measured the energy distributions of the H{sup +} and the H{sup {minus}} ions resulting from the collisional dissociation H{sub 3}{sup +}{r arrow}2H{sup +}+H{sup {minus}} in argon at a projectile energy of 2700 keV. The fragment ions were separated by an analyzing magnet and detected by silicon surface barrier detectors, with the H{sup +} and the H{sup {minus}} ions being detected in coincidence. The energy distributions of the fragments in the projectile center-of-mass frame were extracted from their transverse spatial distributions observed at a position 150 cm downstream from the collision chamber. These distributions were used subsequently to determine the total kinetic energy of the fragments and the correlation angle {theta}{sub 12} between the H{sup +} momenta. A comparison is carried out with recently published data obtained in the low-velocity regime in helium.

On Transient Evolution and Shaping of the Transverse Spatial Distribution of a Light Wave Propagating in a Ring Resonator with Inertial Nonlinear Medium

Abstract The principal properties of the transient evolution and steady state of the system are investigated by constructing the Lyapunov functional. The conditions for stable self-channelling of a light wave, its unlimited spreading, complication and chaos of transverse spatial distribution of radiation are determined.

Novel nonintercepting diagnostic techniques for low-emittance relativistic electron beams

Relativistic electron beams are being generated with emittances low enough that diffraction radiation can be used for beam diagnostics. Techniques based on diffraction radiation can be used to measure the beam transverse momentum distribution and to measure the transverse spatial distribution. The radiation is intense and can be in the visible spectral region where optical diagnostic techniques can be used to maximum advantage.

Resonant self-interaction of CO2laser pulses in SF6

An experimental and numerical investigation was made of the transverse structure of nanosecond CO2 laser pulses propagating in SF6. It was found that resonant self-focusing leads to a considerable distortion in the transverse spatial distribution of the energy density in a pulse having an initial Gaussian profile, this being manifested as a stratification of the beam into concentric annular zones.

Effects of the laser pulse transverse spatial distribution on multiphoton ionization processes

In this paper we study the influence of the transverse spatial distribution of the laser beam on the estimate of the photoionization cross section for the specific case of two-step photoionization (TSPI) of benzene. In particular, we discuss the sensitivity of the inferred cross section on the multimode transverse operation of the dye laser oscillator.

Thin-film aggregate color centers as media for frequency domain optical storage

Thin films of aggregate color centers have been produced by electron and ion irradiation of bulk alkali halide crystals. The transverse spatial distribution of the centers was controlled on a submicron scale using electron lithography. Photochemical hole burning has been accomplished for the first time in a thin film of color centers, using the 6070 A zero-phononN 1 line produced by ion and electron irradiation of NaF crystals.

Form factor in deuteron inelastic screening att≠0

We show that the extension of Gribov inelastic-screening amplitude att≠0, if we use the prescriptions of coherents production for the low-mass part and the triple-Regge formalism for the high-mass part, leads to a sharp discontinuity in the corresponding six-point amplitude and, therefore, a violation of the finite-mass sum rule. This is resolved if we apply the same damping factor of the triple-Regge formalism (essentially the pomeron-hadron residuum) to the low-mass part. This recipe leads to agreement between experiment and theory for the recent ISR data for pd elastic scattering. In the quark-parton model for hadronic diffraction this factor is applied to the whole spectrum of inelastic intermediate diffractive states and is naturally interpreted as Fourier transform of the transverse spatial distribution of the partons in the incident hadron. The presence of this factor is instrumental in eliminating the ambiguity in the duality property of six-point amplitudes, and definitely excludes the abnormal version suggested in the literature.

OPTICAL SELF-PULSING OF JUNCTION LASERS OPERATING CONTINUOUSLY AT ROOM TEMPERATURE

Pulsing of the output light intensity as a result of self-induced second-order mode locking is reported for double-heterostructure (DH) stripe-geometry junction lasers operating continuously at room temperature. In comparison with previously reported results for homostructure lasers operating at low temperatures, the self-induced pulsing in DH lasers occurs at a lower frequency and over a greater range of current and temperature. These differences are attributed to the lower dispersion and lower Q of the laser modes due to the increased temperature and not to the difference in laser structure. In addition, new effects associated with transitions of the mode locking from one modal family to another with different transverse spatial distribution are described.

The diffusion of heat spots in isotropic turbulence

A technique has been developed for the production of small heat spots in the turbulent flow behind bi-plane square-mesh grids, and their distribution downstream of the point of production has been studied using a Wollaston wire-resistance thermometer of response time 0.0002 sec. The transverse spatial distribution function is found to be a Gaussian error function (within the limits of experimental error) at all distances, in agreement with previous results on the temperature wake of a long thin wire. It is possible to determine a mean peak temperature of the spots by measuring the probability that the production of a spot will subsequently raise the temperature at the detector by more than a threshold value as a function of that value. The mean peak temperature is found to decrease with distance downstream more rapidly in turbulent flow than in non-turbulent flow, the observed temperatures being in quantitative agreement with those computed by assuming a spatially uniform rate-of-strain over the volume occupied by the spot. Since the extended spot is too large for this assumption to be literally true, it is concluded that, in the final form, the heat is probably concentrated in a contorted thin layer, and that, following the spot, the shear pattern remains nearly constant in type, decaying aperiodically with the turbulence.