907 research outputs found
A Cryogenic Molecular Ion-Neutral Hybrid Trap
A hybrid trap was developed to confine neutral molecules and molecular ions. We demonstrated the long-term trapping of Stark-decelerated OH radicals in the X 2Pi3/2 (v = 0, J = 3/2, MJ = 3/2, f) state in a permanent magnetic trap. The trap environment was cryogenically cooled to a temperature of 17 K in order to efficiently suppress black-body-radiation-induced pumping of the molecules out of trappable quantum states and collisions with residual background gas molecules which usually limit the trap lifetimes. The cold molecules were kept confined on timescales approaching minutes, an improvement of up to two orders of magnitude compared to room-temperature experiments, at translational temperatures on the order of 25 mK. A cryogenic ion trap was built and laser cooled Ca+ ions were confined. This ion trap can be used to confine sympathetically cooled molecular ions such as N+2or H2O+. Furthermore, a mechanism to superimpose both trap centers by moving the permanent magnets from the magnetic trap over the ion trap was developed. Both traps were characterized and their functionality was proven. The challenges of lasercooling in the strong magnetic field gradients were discussed. The present results pave the way for investigations of cold collisions and reactions with very small reaction rates between molecular ions and neutral molecules, for new avenues for the production of ultracold molecules via sympathetic cooling and for the realization of new forms of hybrid matter with co-trapped atoms or ions
Distribution of particles which produces a "smart" material
If is the scattering amplitude, corresponding to a
potential , where is a bounded domain, and
is the incident plane wave, then we call the radiation
pattern the function , where the unit vector
, the incident direction, is fixed, and , the wavenumber, is
fixed. It is shown that any function , where is the
unit sphere in , can be approximated with any desired accuracy by a
radiation pattern: , where
is an arbitrary small fixed number. The potential ,
corresponding to , depends on and , and can be
calculated analytically. There is a one-to-one correspondence between the above
potential and the density of the number of small acoustically soft particles
, , distributed in an a priori given bounded
domain . The geometrical shape of a small particle is
arbitrary, the boundary of is Lipschitz uniformly with respect to
. The wave number and the direction of the incident upon
plane wave are fixed.It is shown that a suitable distribution of the above
particles in can produce the scattering amplitude ,
, at a fixed , arbitrarily close in the norm of
to an arbitrary given scattering amplitude
, corresponding to a real-valued potential .Comment: corrected typo
- …