On Thompson Problem

In 1987, the second author of this paper reported his conjecture, all finite simple groups $S$ can be characterized uniformly using the order of $S$ and the set of element orders in $S$, to Prof. J. G. Thompson. In their communications, Thompson posed his problem about the judgment of solvability of finite groups $G$. In this paper we give a positive answer for Thompson's problem if the prime graph of $G$ is not connection.Comment: 8 page

Observation of electric-dipole transitions in the laser-cooling candidate Th- And its application for cooling antiprotons

Despite the fact that the laser-cooling method is a well-established technique to obtain ultracold neutral atoms and atomic cations, it has rarely if ever been applied to atomic anions due to the lack of suitable electric-dipole transitions. Efforts of more than a decade have until recently only resulted in La- as a promising anion candidate for laser cooling, but our previous work [Tang et al., Phys. Rev. Lett. 123, 203002 (2019)10.1103/PhysRevLett.123.203002] showed that Th- is also a potential candidate. Here we report on a combination of experimental and theoretical studies to determine the frequencies and rates, as well as branching ratios, for the relevant transitions in Th-. The resonant frequency of the laser-cooling transition is determined to be ν=123.455(30) THz [λ=2428.4(6)nm]. The transition rate is calculated as A=1.17×104s-1. Since the branching fraction to dark states is negligible, 1.47×10-10, this represents an ideal closed cycle in Th- for laser cooling. Furthermore, the zero nuclear spin of Th232 makes the cooling process possible in a Penning trap, which can be used to confine both antiprotons and Th- ions. The presented ion dynamics simulations show that the laser-cooled Th- anions can effectively cool antiprotons to a temperature around 10 mK

Candidate for Laser Cooling of a Negative Ion : High-Resolution Photoelectron Imaging of Th

Laser cooling is a well-established technique for the creation of ensembles of ultracold neutral atoms or positive ions. This ability has opened many exciting new research fields over the past 40 years. However, no negatively charged ions have been directly laser cooled because a cycling transition is very rare in atomic anions. Efforts of more than a decade currently have La- as the most promising candidate. We report on experimental and theoretical studies supporting Th- as a new promising candidate for laser cooling. The measured and calculated electron affinities of Th are, respectively, 4901.35(48) cm-1 and 4832 cm-1, or 0.607 690(60) and 0.599 eV, almost a factor of 2 larger than the previous theoretical value of 0.368 eV. The ground state of Th- is determined to be 6d37s2 F43/2e rather than 6d27s27p G45/2o. The consequence of this is that there are several strong electric dipole transitions between the bound levels arising from configurations 6d37s2 and 6d27s27p in Th-. The potential laser-cooling transition is S1/2o2↔F43/2e with a wavelength of 2.6 μm. The zero nuclear spin and hence lack of hyperfine structure in Th- reduces the potential complications in laser cooling as encountered in La-, making Th- a new and exciting candidate for laser cooling

Growth of SnSe single crystal via vertical vapor deposition method and characterization of its thermoelectric performance

In this work, a vertical vapor deposition method was developed to grow SnSe single crystals. More than thirty single crystal particles were simultaneously obtained and the largest size could up to 15 x 15 x 10 mm(3). The as-grown crystal is tested has nearly Sn: Se = 1: 1 stoichiometric ratio and demonstrates standard orthorhombic Pnma space group at room temperature. Electrical transport measurement shows the present SnSe single crystal has a largest electrical conductivity sigma = 39.6 S cm(-1) near Pnma- Cmcm phase transition temperature, and the maximum Seebeck coefficient S = 566 mu NK-1 is taken place around 580 K. Thermal transport analysis implies SnSe single crystal exhibits a lowest total thermal conductivity k(tot) = 0.44 Wm(-1) K-1 near Pnma- Cmcm phase transition. Finally, it is calculated the figure of merit ZT has a largest value similar to 1.0 around 800 K that implies SnSe single crystal is a promising middle- temperature TE material