Anisotropic sub-Doppler laser cooling in dysprosium magneto-optical traps

Magneto-optical traps (MOTs) of Er and Dy have recently been shown to exhibit population-wide sub-Doppler cooling due to their near degeneracy of excited and ground state Lande g factors. We discuss here an additional, unusual intra-MOT sub-Doppler cooling mechanism that appears when the total Dy MOT cooling laser intensity and magnetic quadrupole gradient increase beyond critical values. Specifically, anisotropically sub-Doppler-cooled cores appear, and their orientation with respect to the quadrupole axis flips at a critical ratio of the MOT laser intensity along the quadrupole axis versus that in the plane of symmetry. This phenomenon can be traced to a loss of the velocity-selective resonance at zero velocity in the cooling force along directions in which the atomic polarization is oriented by the quadrupole field. We present data characterizing this anisotropic laser cooling phenomenon and discuss a qualitative model for its origin based on the extraordinarily large Dy magnetic moment and Dy's near degenerate g factors.Comment: 4 pages, 5 figure

Collective Aspects of Mitigating Interactions Between Large Carnivores and Humans

Understanding how to coexist with wildlife is of critical importance for successful conservation, particularly for large carnivores, who pose risks to human safety, livestock, and game species. In Montana (USA), black and grizzly bears occur across much of the western half of the state. In particular, grizzly bears are protected by the Endangered Species Act and their populations and ranges are expanding, resulting in increased overlap between humans and bears. Interactions with bears can be mitigated when landowners take certain actions to secure bear attractants – such as using bear resistant garbage cans and feed storage, using electric fences, removing livestock carcasses, and taking down bird feeders in the spring and fall. Few studies have examined what drives uptake of these actions, but factors include perceived risks and benefits and personal experience at the individual level. This research aims to understand how individual and collective aspects drive uptake of actions to secure bear attractants. We administered a mail-back questionnaire to Montana landowners and used the collective interest model to determine the relative effects of collective and individual factors in influencing whether landowners secure bear attractants. We developed logistic regression models for each behavior. Collective aspects that drove behavior included social norms (i.e., what individuals think they should do and what others are doing) and network centrality (i.e., how much social influence an individual has). This research suggests that outreach campaigns that only highlight the risks of large carnivores could be substantially improved by describing the collective aspects of mitigation

Coherent Control of Trapped Bosons

We investigate the quantum behavior of a mesoscopic two-boson system produced by number-squeezing ultracold gases of alkali metal atoms. The quantum Poincare maps of the wavefunctions are affected by chaos in those regions of the phase space where the classical dynamics produces features that are comparable to hbar. We also investigate the possibility for quantum control in the dynamics of excitations in these systems. Controlled excitations are mediated by pulsed signals that cause Stimulated Raman Adiabatic passage (STIRAP) from the ground state to a state of higher energy. The dynamics of this transition is affected by chaos caused by the pulses in certain regions of the phase space. A transition to chaos can thus provide a method of controlling STIRAP.Comment: 17 figures, Appended a paragraph on section 1 and explained details behind the hamiltonian on section

Structural dichroism in the antiferromagnetic insulating phase of V_2O_3

We performed near-edge x-ray absorption spectroscopy (XANES) at V K edge in the antiferromagnetic insulating (AFI) phase of a 2.8% Cr-doped V_2O_3 single crystal. Linear dichroism of several percent is measured in the hexagonal plane and found to be in good agreement with ab-initio calculations based on multiple scattering theory. This experiment definitively proves the structural origin of the signal and therefore solves a controversy raised by previous interpretations of the same dichroism as non-reciprocal. It also calls for a further investigation of the role of the magnetoelectric annealing procedure in cooling to the AFI phase.Comment: 4 pages 3 figures. To be published in Phys. Rev. B (2005