82 research outputs found
State-insensitive bichromatic optical trapping
We propose a scheme for state-insensitive trapping of neutral atoms by using
light with two independent wavelengths. In particular, we describe the use of
trapping and control lasers to minimize the variance of the potential
experienced by a trapped Rb atom in ground and excited states. We present
calculated values of wavelength pairs for which the 5s and 5p_{3/2} levels have
the same ac Stark shifts in the presence of two laser fields.Comment: 5 pages, 4 figure
Blackbody radiation shift in a 43Ca+ ion optical frequency standard
Motivated by the prospect of an optical frequency standard based on 43Ca+, we
calculate the blackbody radiation (BBR) shift of the 4s_1/2-3d_5/2 clock
transition, which is a major component of the uncertainty budget. The
calculations are based on the relativistic all-order single-double method where
all single and double excitations of the Dirac-Fock wave function are included
to all orders of perturbation theory. Additional calculations are conducted for
the dominant contributions in order to evaluate some omitted high-order
corrections and estimate the uncertainties of the final results. The BBR shift
obtained for this transition is 0.38(1) Hz. The tensor polarizability of the
3d_5/2 level is also calculated and its uncertainty is evaluated as well. Our
results are compared with other calculations.Comment: 4 page
Accurate determination of electric-dipole matrix elements in K and Rb from Stark shift measurements
Stark shifts of potassium and rubidium D1 lines have been measured with high
precision by Miller et al [1]. In this work, we combine these measurements with
our all-order calculations to determine the values of the electric-dipole
matrix elements for the 4p_j-3d_j' transitions in K and for the 5p_j-4d_j'
transitions in Rb to high precision. The 4p_1/2-3d_3/2 and 5p_1/2-4d_3/2
transitions contribute on the order of 90% to the respective polarizabilities
of the np_1/2 states in K and Rb, and the remaining 10% can be accurately
calculated using the relativistic all-order method. Therefore, the combination
of the experimental data and theoretical calculations allows us to determine
the np-(n-1)d matrix elements and their uncertainties. We compare these values
with our all-order calculations of the np-(n-1)d matrix elements in K and Rb
for a benchmark test of the accuracy of the all-order method for transitions
involving nd states. Such matrix elements are of special interest for many
applications, such as determination of magic wavelengths in alkali-metal atoms
for state-insensitive cooling and trapping and determination of blackbody
radiation shifts in optical frequency standards with ions.Comment: 5 page
Recommended from our members
Modeling and development of fabrication method for embedding membrane based microvalve in bulk microfluidic device
PDMS membrane-based microvalves are becoming increasingly more important for the control of fluid flow within MECS applications such as microreactors used to synthesize nanoparticles and biological macromolecules. The motivation for pursuing PDMS membrane-based microvalves is for implementing a plug flow microreactor to simulate slug flow yielding a narrower residence time distribution (RTD). Barriers to the use of PDMS membrane-based microvalves within these types of MECS applications include the need to be scalable and compact, capable of operating at higher pressures in a variety of solvents. Most current bonding architectures for PDMS membrane-based microvalves are limited to one atmosphere.
This research work describes the design, analysis, fabrication, and characterization of PDMS membrane-based microvalve architecture for implementation within MECS devices for nanoparticles synthesis applications. The new fabrication approach is to make reliable bonds capable of withstanding higher pressures. The approach developed in this thesis eliminates bonding constraints within current PDMS bonding architectures (e.g. bonding of dissimilar materials and stress distribution problems) through the use of sealing bosses and enables further miniaturization of the overall structure by entrapping the membrane between stiff polymer substrates.
A novel fabrication method has been developed for embedding PDMS membrane-based microvalves in multi-layer, arrayed microfluidic devices. This novel architecture sandwiches an elastomeric membrane between polycarbonate substrates having sealing bosses and can withstand operating pressure upto 100 psi. This meets a key requirement for MECS device architectures which require higher fluidic pressures in a chemical processing. In addition, the architecture incorporates the use of stiff polymers which can reduce the overall size of the device. Based on the fact that a polycarbonate lamina has an elastic modulus 1000 times that of a PDMS lamina (currently used in multi-layer valve architectures), plate mechanics would predict a 10 fold reduction in the thickness of those laminae to achieve the same stiffness within the stack
Electric Quadrupole Moments of Metastable States of Ca+, Sr+, and Ba+
Electric quadrupole moments of the metastable nd3/2 and nd5/2 states of Ca+,
Sr+, and Ba+ are calculated using the relativistic all-order method including
all single, double, and partial triple excitations of the Dirac-Hartree-Fock
wave function to provide recommended values for the cases where no experimental
data are available. The contributions of all non-linear single and double terms
are also calculated for the case of Ca+ for comparison of our approach with the
CCSD(T) results. The third-order many body perturbation theory is used to
evaluate contributions of high partial waves and the Breit interaction. The
remaining omitted correlation corrections are estimated as well. Extensive
study of the uncertainty of our calculations is carried out to establish
accuracy of our recommended values to be 0.5% - 1% depending on the particular
ion. Comprehensive comparison of our results with other theoretical values and
experiment is carried out. Our result for the quadrupole moment of the 3d5/2
state of Ca+ ion, 1.849(17)ea_0^2, is in agreement with the most precise recent
measurement 1.83(1)ea_0^2 by Roos et al. [Nature 443, 316 (2006)].Comment: 7 page
Magic wavelengths for the np-ns transitions in alkali-metal atoms
Extensive calculations of the electric-dipole matrix elements in alkali-metal
atoms are conducted using the relativistic all-order method. This approach is a
linearized version of the coupled-cluster method, which sums infinite sets of
many-body perturbation theory terms. All allowed transitions between the lowest
ns, np_1/2, np_3/2 states and a large number of excited states are considered
in these calculations and their accuracy is evaluated. The resulting
electric-dipole matrix elements are used for the high-precision calculation of
frequency-dependent polarizabilities of the excited states of alkali-metal
atoms. We find magic wavelengths in alkali-metal atoms for which the ns and
np_1/2 and np_3/2 atomic levels have the same ac Stark shifts, which
facilitates state-insensitive optical cooling and trapping.Comment: 12 pages, 8 figure
Magic-zero wavelengths of alkali-metal atoms and their applications
Using first-principles calculations, we identify "magic-zero" optical
wavelengths, \lambda_zero, for which the ground-state frequency-dependent
polarizabilities of alkali-metal atoms vanish. Our approach uses
high-precision, relativistic all-order methods in which all single, double, and
partial triple excitations of the Dirac-Fock wave functions are included to all
orders of perturbation theory. We discuss the use of magic-zero wavelengths for
sympathetic cooling in two-species mixtures of alkalis with group-II and other
elements of interest. Special cases in which these wavelengths coincide with
strong resonance transitions in a target system are identified.Comment: 6 page
Blackbody-radiation shift in a 88Sr+ ion optical frequency standard
The blackbody radiation (BBR) shift of the 5s - 4d_{5/2} clock transition in
88Sr+ is calculated to be 0.250(9) Hz at room temperature, T=300K, using the
relativistic all-order method where all single and double excitations of the
Dirac-Fock wave function are included to all orders of perturbation theory. The
BBR shift is a major component in the uncertainty budget of the optical
frequency standard based on the 88Sr+ trapped ion. The scalar polarizabilities
of the 5s and 4d_{5/2} levels, as well as the tensor polarizability of the
4d_{5/2} level, are presented together with the evaluation of their
uncertainties. The lifetimes of the 4d_{3/2}, 4d_{5/2}, 5p_{1/2}, and 5p_{3/2}
states are calculated and compared with experimental values.Comment: 6 page
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