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Register a new userIP determination and 1+1 REMPI spectrum of SiO at 210-220 nm with implications for SiO$^{+}$ ion trap loading
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Added by
Patrick Stollenwerk
Publication date
2017
fields
Physics
and research's language is
English
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The 1+1 REMPI spectrum of SiO in the 210-220 nm range is recorded. Observed bands are assigned to the $A-X$ vibrational bands $(v``=0-3, v`=5-10)$ and a tentative assignment is given to the 2-photon transition from $X$ to the n=12-13 $[X^{2}{Sigma}^{+},v^{+}=1]$ Rydberg states at 216-217 nm. We estimate the IP of SiO to be 11.59(1) eV. The SiO$^{+}$ cation has previously been identified as a molecular candidate amenable to laser control. Our work allows us to identify an efficient method for loading cold SiO$^{+}$ from an ablated sample of SiO into an ion trap via the $(5,0)$ $A-X$ band at 213.977 nm.
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The dispersed fluorescence following pulsed dye laser excitation of the $textrm{B}_2 Sigma^+ - textrm{X}^2 Sigma^+(0,0)$ band of a cold sample of SiO$^+$ has been recorded and analyzed. The branching ratios for $textrm{B}_2 Sigma^+ (v=0) rightarrow textrm{X}^2 Sigma^+(v)$ and $textrm{B}_2 Sigma^+ (v=0) rightarrow textrm{A}^2 Pi_i(v)$ emission were determined and compared with values predicted based upon existing experimental and theoretical data. The experimentally determined branching ratios show that the $textrm{B}_2 Sigma^+ (v=0) rightarrow textrm{X}^2 Sigma^+(v)$ transitions are somewhat less diagonal than predicted. The implications for laser cooling of a trapped sample of SiO$^+$ using broadband laser excitation are discussed.
Neutral Ytterbium (YbI) and singly ionized Ytterbium (YbII) is widely used in experiments in quantum optics, metrology and quantum information science. We report on the investigation of isotope selective two-photoionisation of YbI that allows for efficient loading of ion traps with YbII. Results are presented on two-colour (399 nm and 369 nm) and single-colour (399 nm) photoionisation and their efficiency is compared to electron impact ionisation. Nearly deterministic loading of a desired number of YbII ions into a linear Paul trap is demonstrated.
We demonstrate an efficient scheme for continuous trap loading based upon spatially selective optical pumping. We discuss the case of $^{1}$S$_{0}$ calcium atoms in an optical dipole trap (ODT), however, similar strategies should be applicable to a wide range of atomic species. Our starting point is a reservoir of moderately cold ($approx 300 mu$K) metastable $^{3}$P$_{2}$-atoms prepared by means of a magneto-optic trap (triplet-MOT). A focused 532 nm laser beam produces a strongly elongated optical potential for $^{1}$S$_{0}$-atoms with up to 350 $mu$K well depth. A weak focused laser beam at 430 nm, carefully superimposed upon the ODT beam, selectively pumps the $^{3}$P$_{2}$-atoms inside the capture volume to the singlet state, where they are confined by the ODT. The triplet-MOT perpetually refills the capture volume with $^{3}$P$_{2}$-atoms thus providing a continuous stream of cold atoms into the ODT at a rate of $10^7 $s$^{-1}$. Limited by evaporation loss, in 200 ms we typically load $5 times 10^5$ atoms with an initial radial temperature of 85 $mu$K. After terminating the loading we observe evaporation during 50 ms leaving us with $10^5$ atoms at radial temperatures close to 40 $mu$K and a peak phase space density of $6.8 times 10^{-5}$. We point out that a comparable scheme could be employed to load a dipole trap with $^{3}$P$_{0}$-atoms.
We have constructed a magneto-optical trap (MOT) for metastable triplet helium atoms utilizing the 2 3S1 -> 3 3P2 line at 389 nm as the trapping and cooling transition. The far-red-detuned MOT (detuning Delta = -41 MHz) typically contains few times 10^7 atoms at a relatively high (~10^9 cm^-3) density, which is a consequence of the large momentum transfer per photon at 389 nm and a small two-body loss rate coefficient (2 * 10^-10 cm^3/s < beta < 1.0 * 10^-9 cm^3/s). The two-body loss rate is more than five times smaller than in a MOT on the commonly used 2 3S1 -> 2 3P2 line at 1083 nm. Furthermore, we measure a temperature of 0.46(1) mK, a factor 2.5 lower as compared to the 1083 nm case. Decreasing the detuning to Delta= -9 MHz results in a cloud temperature as low as 0.25(1) mK, at small number of trapped atoms. The 389 nm MOT exhibits small losses due to two-photon ionization, which have been investigated as well.
We have demonstrated that the ion current resulting from collisions between metastable krypton atoms in a magneto-optical trap can be used to precisely measure the trap loading rate. We measured both the ion current of the abundant isotope Kr-83 (isotopic abundance = 11%) and the single-atom counting rate of the rare isotope Kr-85 (isotopic abundance ~ 1x10^-11), and found the two quantities to be proportional at a precision level of 0.9%. This work results in a significant improvement in using the magneto-optical trap as an analytical tool for noble-gas isotope ratio measurements, and will benefit both atomic physics studies and applications in the earth sciences.
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