Multiple Breakup Research Articles

Satellite and subsatellite formation in capillary breakup

An investigation of the interfacial-tension-driven fragmentation of a very long fluid filament in a quiescent viscous fluid is presented. Experiments covering almost three orders of magnitude in viscosity ratio reveal as many as 19 satellite droplets in between the largest droplets; complementary boundary-integral calculations are used to study numerically the evolution of the filament as a function of the viscosity ratio of the fluids and the initial wavenumber of the interface perturbation. Satellite drops are generated owing to multiple breakup sequences around the neck region of a highly deformed filament. In low-viscosity ratio systems, p < O(0.1), the breakup mechanism is self-repeating in the sense that every pinch-off is always associated with the formation of a neck, the neck undergoes pinch-off, and the process repeats. In general the agreement between computations and experiments is excellent; both indicate that the initial wavenumber of the disturbance is important in the quantitative details of the generated drop size distributions. However, these details are insignificant when compared with the large variations produced in the drop size distributions owing to variation in the viscosity ratio.

Projectile excitation energy evolution in peripheral collisions for 16O + 197Au at 32.5, 50 and 70 MeV/N

A comparison of the multiple breakup of 16O projectiles scattered by a Au target at three different energies (32.5, 50 and 70 MeV/N) is presented. The excitation energy spectra of the primary projectile-like nuclei decaying into specific output channels were reconstructed. The excitation energy of the target is found to increase faster with beam energy than the one for the quasi-projectile.

Excitation and multiple dissociation of 12C, 14N, and 16O projectiles in peripheral collisions at 32.5 MeV/nucleon.

Cross sections for the multiple breakup of $^{16}\mathrm{O}$, $^{14}\mathrm{N}$, and $^{12}\mathrm{C}$ projectiles scattered by an Au target were measured with an array of 34 phoswich detectors. The dissociation of the projectiles into as many as five charged particles has been observed. The yields of different exit channels correlate approximately with the threshold energy for separation of the projectile into the observed fragments. The excitation spectrum of the primary projectile-like nucleus was reconstructed from the measured positions and kinetic energies of the individual fragments. The energy sharing between projectile and target is consistent with a fast excitation mechanism in which differential increases in projectile excitation energy appear to be accompanied by comparable increases in target excitation. Calculations of the yields based on a sequence of binary decays are presented.

On the stability of coagulation—fragmentation population balances

When coagulation and fragmentation both occur in a system, the competition between these processes may lead to a steady-state size distribution. We consider some specific moment solutions to a generalized coagulation-fragmentation population balance equation (in which multiple breakup is allowed) in order to determine when it is may be possible for such steady states to exist. Steady states occur for systems with homogeneous rate kernels of order β (fragmentation) and λ (coagulation) that satisfy β − λ + 1 > 0. Finally, we discuss the applicability of scaling to this generalized coagulation-fragmentation population balance.

Excitation and multiple dissociation of 16O, 14N and 12C projectiles at 32.5 MeV per nucleon

The cross sections for the multiple breakup of 16O, 14N and 12C projectiles scattered by a Au target were measured with an array of 34 detectors. The excitation spectrum of the primary projectile-like nucleus was reconstructed from the measured positions and kinetic energies of the individual fragments. Calculations of the yields based on a sequence of binary decays are presented.

Multifragmentation and evaporation: Two competing processes in intermediate energy nuclear collisions

We study the conditions at which multiple break-up of nuclei occurs during a collision. A minimal temperature of about 5 MeV seems to be necessary to produce multifragmentation. The average number of fragments produced is correlated with the average number of primary nucleon-nucleon collisions. Based on these ideas a simple model of evaporation-multifragmentation reactions is developed, which accounts for most of the existing data for protons and heavy ions induced reactions.

Time dependent formulation of polyatomic photofragmentation: Application to H3+

We present a new approach to photofragmentation which through its explicit time dependence avoids the difficulties normally associated with calculation of Franck–Condon processes. No scattering eigenfunctions or Franck–Condon overlaps are required, yet the formulae are exact within the same assumptions as the usual time independent theory. Semiclassical implementation of the method is described in connection with a successful application to H+3, which involves, in our model, a multiple continuum breakup final state on one of two excited state surfaces treated. Full arrangement and energy partitioning information are given on both surfaces in a calculation whose main numerical effort involves running five classical trajectories.

Two-photon self-induced transparency in a resonant medium. II. Transient pulse behaviour

For pt.I see ibid., vol.8, no.3, 339 (1975). The transient behaviour of two short optical pulses in two-photon coherent propagation is obtained by calculating numerically the coherent propagation equations which couple the two electromagnetic pulses and the atomic system in self-consistent fashion. The coherent interaction of the two different frequency pulses gives rise to lossless propagation in the absorptive medium. This description is characterized by a two-photon area theorem. Novel coherent propagation effects of peak amplification and multiple pulse breakup are found. These effects are ascribed to two-photon self-induced transparency analogous to that of a one-photon transition in a two-level system. A difference of input intensity between the two different frequency pulses yields curious modulation effects involving sharp peak amplification and marked pulse breakup for the low-intensity input. In contrast, the high-intensity input pulse displays a smooth variation with distance and time. Low-loss pulse transmission above threshold, and pulse advance and delay are found for the present case in contrast to that for one-photon self-induced transparency.

Peak Amplification and Breakup of a Coherent Optical Pulse in a Simple Atomic Absorber

We report the low-loss propagation, peak amplification, and multiple breakup of a coherent laser pulse undergoing self-induced transparency by interacting with two nondegenerate levels of a highly absorbing gas of Rb atoms. These results are in good agreement with computer solutions of coupled Schr\"odinger and Maxwell equations including relaxation.