Correlation dynamics between electrons and ions in the fragmentation of D2_2 molecules by short laser pulses

We studied the recollision dynamics between the electrons and D$_2^+$ ions following the tunneling ionization of D$_2$ molecules in an intense short pulse laser field. The returning electron collisionally excites the D$_2^+$ ion to excited electronic states from there D$_2^+$ can dissociate or be further ionized by the laser field, resulting in D$^+$ + D or D$^+$ + D$^+$, respectively. We modeled the fragmentation dynamics and calculated the resulting kinetic energy spectrum of D$^+$ to compare with recent experiments. Since the recollision time is locked to the tunneling ionization time which occurs only within fraction of an optical cycle, the peaks in the D$^+$ kinetic energy spectra provides a measure of the time when the recollision occurs. This collision dynamics forms the basis of the molecular clock where the clock can be read with attosecond precision, as first proposed by Corkum and coworkers. By analyzing each of the elementary processes leading to the fragmentation quantitatively, we identified how the molecular clock is to be read from the measured kinetic energy spectra of D$^+$ and what laser parameters be used in order to measure the clock more accurately.Comment: 13 pages with 14 figure

Recollisions, bremsstrahlung, and attosecond pulses from intense laser fields

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Control of high-order harmonic generation in strong laser fields

Using solutions of the time-dependent Schr\uf6dinger equation for the H2+ molecular ion, we examine various scenarios for controlling high-order harmonic generation with combinations of laser fields. It is found that (i) the harmonic generation ''plateau'' can be modified by combining a laser field with its third harmonic field, (ii) even harmonics are controllable using the combination of a laser field and a weaker second harmonic field, and (iii) the phases of high-order harmonics in a strong driving field can also be changed by additional fields. In particular, when a weak dc electric field is applied, we prove that the phase shifts of all harmonics linearly depend on the dc field strength. In addition, when an ultrastrong static magnetic field is applied collinearly with the driving laser polarization, harmonic generation efficiency is enhanced and higher harmonics beyond the usual ''cutoff'' are generated as a result of the squeezing of the transversely spreading electron wave packets. The enhancement is a confirmation of the electron-ion recollision mechanism for high-order harmonic generation.Peer reviewed: YesNRC publication: Ye

Surgical intervention of severe post-ERCP-pancreatitis accompanied with duodenum perforation*

Endoscopic retrograde cholangiopancreatography (ERCP) is a procedure widely used to diagnose and treat conditions of biliary or pancreatic ductal system. The post-ERCP severe acute pancreatitis (SAP) accompanied with duodenum perforation is rare but serious, remaining a challenge in clinic. In this study we report two such cases. Two Chinese women were treated for clinical suspicion of bile duct obstruction and underwent ERCP after admission. Both developed duodenum perforation and SAP after ERCP, and were managed in the intensive care unit (ICU) and required an organ-failure support. The surgical intervention of the peri-pancreatic debridement with lumber-abdominal compound incisions and postoperative washing and drainage was performed, and the two patients recovered well. The therapeutic effect of the peri-pancreatic debridement with lumber-abdominal compound incisions combined with postoperative washing and drainage in the patients of severe post-ERCP-pancreatitis (PEP) and duodenum perforation is satisfactory

Attosecond science

Attosecond technology builds on, and contributes to, important historic directions in science. For this reason, the science has the depth to yield important discoveries for a long time. Unfortunately the title "attosecond" science biases us to think mostly about dynamics but many of the most important applications of "attosecond technology" may not be related to dynamics at all. This broad set of applications point to the future impact of the technology.Peer reviewed: YesNRC publication: Ye