We present the realisation of a magneto-optical trap for chromium. 52Cr atoms are loaded directly from a thermal beam. The trap lifetime is enhanced by using two red lasers to repump population that has decayed, via intercombination lines, to metastable levels back into the cooling cycle. We have measured the wavelengths of these intercombination lines and observed coherent Raman spectra. The observed density of 108 cm−3 is currently limited by collisions with the hot beam.
We present our results on the realization of a magneto-optical trap (MOT) for chromium atoms with repumpers on two intercombination lines. The high magnetic moment (6 Bohr magneton) and the isotopic composition of chromium are promising for investigation of collective quantum statistical effects in ultracold Bose-and Fermigases in steep magnetic traps. Chromium is also interesting in view of its applications in atom lithography. Some lo6 bosonic 52Cr atoms were trapped in a standard six beam o+/d-configuration directly out of a thermal chromium beam (T=1500-1700 K). Typically 50mW of laser power were used to drive the 7S3-7P4 transition (hd25nm) for the magneto-optical trap. We measured the loading curve by detecting the fluorescence of the trapped atoms with a CCD camera. From this data we extracted the lifetime (z=40ms) of the MOT. The MOT transition is not closed, since atoms in the P4 state can decay via weak intercombination lines to two metastable levels (' D3.4). To increasing the lifetime of the trap repumping lasers need to be applied to close these loss channels. Two grating stabilized diode lasers locked to a passively stabilized external resonator were set up to accomplish this. Enhancement factors (=fluorescence with repumpers / fluorescence without repumpers) of up to 40 were achieved. We studied the effect of the repumpers and observed coherent Raman spectra for the 5D3,4-7P4 repumping transition'.We determined the lifetime of the trap with repumpers on resonance (2=318ms) and the decay rate into the metastable levels (r=200s"). Since this decay rate is smaller than expected, we changed the repumping transition from 5D3.4-7P4 to the faster (r=6000s-') 5D3,4-7P3 transition. Recently we installed a Zeeman slower technique to capture atoms with initial velocities smaller than 500 m/s and observed magnetic trapping in the magnetic field of the MOT coils. In future experiments we plan to trap also the fermionic isotope, characterize the collisional properties of chromium and proceed with evaporative cooling to the degenerate regime. 7 'A. S. Bell, J. Stuhler, S. Locher, S. Hensler, J. Mlynek, and T. Pfau, A magneto-optical trap for chromium atoms with population repumping via intercombination lines, Euruphvs. Left., 45 (2), pp. 156-161 (1999) 0-7803-5661 -6 I 99 I $1 0.00 0 1999 IEEE
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.