A Fast Radio Burst Search Method for VLBI Observation

We introduce the cross spectrum based FRB (Fast Radio Burst) search method for VLBI observation. This method optimizes the fringe fitting scheme in geodetic VLBI data post processing, which fully utilizes the cross spectrum fringe phase information and therefore maximizes the power of single pulse signals. Working with cross spectrum greatly reduces the effect of radio frequency interference (RFI) compared with using auto spectrum. Single pulse detection confidence increases by cross identifying detections from multiple baselines. By combining the power of multiple baselines, we may improve the detection sensitivity. Our method is similar to that of coherent beam forming, but without the computational expense to form a great number of beams to cover the whole field of view of our telescopes. The data processing pipeline designed for this method is easy to implement and parallelize, which can be deployed in various kinds of VLBI observations. In particular, we point out that VGOS observations are very suitable for FRB search.Comment: Accepted for publication in A

Possible link of a structurally driven spin flip transition and the insulator-metal transition in the perovskite La1−x_{1-x}Bax_{x}CoO3_{3}

The complex nature of the magnetic ground state in La$_{1-x}$A$_{x}$CoO$_{3}$ (A = Ca, Sr, Ba) has been investigated via neutron scattering. It was previously observed that ferromagnetic (FM) as well as antiferromagnetic (AFM) correlations can coexist prior to the insulator-metal transition (IMT). We focused on a unique region in the Ba phase diagram, from x = 0.17 - 0.22, in which a commensurate AFM phase appears first with a propagation vector, k = (0, -0.5, 0.5), and the Co moment in the (001)$_{R}$ plane of the rhombohedral lattice. With increasing x, the AFM component weakens while an FM order appears with the FM Co moment directed along the (001)$_{R}$ (=(111)$_{C}$) axis. By x = 0.22, a spin flip to new FM component appears as the crystal fully transforms to an orthorhombic (Pnma) structure, with the Co moments pointing along a new direction, (001)$_{O}$ (=(110)$_{C}$). It is the emergence of the magnetic Pnma phase that leads to IMT.Comment: 5 page

3,4-Dimethyl­anilinium 4-methyl­benzene­sulfonate

In the crystal structure of the title compound, C8H12N+·C7H7O3S−, N—H⋯O hydrogen bonds link the cations and anions into ribbons parallel to the c axis. N—H⋯S inter­actions also occur

Creation and control of a single coherent attosecond xuv pulse by few-cycle intense laser pulses

This is the published version, also available here: http://dx.doi.org/10.1103/PhysRevA.74.023404.We present ab initio quantum and classical investigations on the production and control of a single attosecond pulse by using few-cycle intense laser pulses as the driving field. The high-harmonic-generation power spectrum is calculated by accurately and efficiently solving the time-dependent Schrödinger equation using the time-dependent generalized pseudospectral method. The time-frequency characteristics of the attosecond xuv pulse are analyzed in detail by means of the wavelet transform of the time-dependent induced dipole. To better understand the physical processes, we also perform classical trajectory simulation of the strong-field electron dynamics and electron returning energy map. We found that the quantum and classical results provide complementary and consistent information regarding the underlying mechanisms responsible for the production of the coherent attosecond pulse. For few-cycle (5fs) driving pulses, it is shown that the emission of the consecutive harmonics in the supercontinuum cutoff regime can be synchronized and locked in phase resulting in the production of a coherent attosecond pulse. Moreover, the time profile of the attosecond pulses can be controlled by tuning the carrier envelope phase

Very-high-order harmonic generation from Ar atoms and Ar+ ions in superintense pulsed laser fields: An ab initio self-interaction-free time-dependent density-functional approach

This is the published version, also available here: http://dx.doi.org/10.1103/PhysRevA.71.063813.We present an ab initio nonpertubative investigation of the mechanisms responsible for the production of very-high-order harmonic generation (HHG) from Ar atoms and Ar+ ions by means of the self-interaction-free time-dependent density-functional theory recently developed. Further, by introducing an effective charge concept, we can study at which laser intensity the contribution to the high-energy HHG from Ar+ ions precede over the Ar atoms. Comparing the HHG behavior from Ar atoms and Ar+ ions in the superintense laser field, we conclude that the high-energy HHG observed in the recent experiment originated from the ionized Ar atoms

4-[(2′-Cyano­biphenyl-4-yl)meth­yl]morpholin-4-ium hexa­fluoridophosphate

In the cation of the title compound, C18H19N2O+·PF6 −, the morpholine ring adopts the usual chair conformation and the dihedral angle between the benzene rings is 67.55 (11)°. The F atoms of the anion are disordered over two orientations with a refined occupancy ratio of 0.65 (2):0.35 (2). In the crystal, inter­molecular N—H⋯N hydrogen bonds link the cations into chains parallel to the c axis. The crystal packing is further enforced by inter­ionic C—H⋯F hydrogen bonds