Gaussian-type Distributions Research Articles

Comparison of Moments for Classical‐, Quasi‐, and Convolution‐Fickian Dispersion of a Conservative Tracer

Transport moments up to fourth order for convolution‐, quasi‐, and classical‐Fickian dispersion of a conservative tracer are presented and compared. Convolution‐Fickian yields a non‐Gaussian distribution while quasi‐ and classical‐Fickian result in Gaussian type distributions regardless of the distribution of a stationary velocity field. The first and second central spatial moments are the same for convolution‐ and quasi‐Fickian dispersion, while the third and fourth central moments differ.

Mapping of parent transition-state wave functions into product rotations: An experimental and theoretical investigation of the photodissociation of FNO

We study experimentally and theoretically reflection-type structures in the rotational distributions of NO following the photodissociation of FNO via excitation of the S1 state. Exciting quasibound states with zero quanta of bending vibration in the FNO(S1) state yields Gaussian-type rotational distributions, while excitation of states with one bending quantum leads to bimodal distributions. In the latter case, the ratio of the two intensity maxima depends on the number of NO stretching quanta in the S1 state. The accompanying calculations employing a three-dimensional ab initio potential energy surface for the S1 state of FNO are performed in the time-dependent wave packet approach. They reproduce the main features of the experimental distributions, especially the bimodality. The analysis of two-dimensional calculations for a frozen NO bond distance shows that the final rotational state distributions can be explained as the result of a dynamical mapping of the stationary wave function on the transition line onto the fragment rotational quantum number axis. Here the transition line is defined as the line which separates the inner part of the FNO(S1) potential energy surface from the strongly repulsive F+NO product channel.

Kinematical analysis of the experimental data on nucleus-nucleus collisions at 800 MeV/nucleon

A purely empirical kinematical analysis of the existing data on nucleus-nucleus collisions at the beam energy of 800 MeV/nucleon is presented. We searched for a moving frame (frames) in which particles are emitted symmetrically about 90°, and found that three frames might exist in the mid-rapidity region. For nearly equal-mass collisions the rapidities of these frames are 0.22, 0.62 and 1.02. Emission of nuclear fragments in each frame has been studied. The cross section is factorized as a product of two gaussian-type distributions, one which involves only p T and the other which involves only p L, where p T and p L are the transverse and longitudinal momenta, respectively, measured in that frame. The present result is compared with the participantspectator model. We propose two new sources which lie close to the projectile and target rapidities but have different natures from the spectator.