961 research outputs found
Wavelength dependent ac-Stark shift of the 1S0 - 3P1 transition at 657 nm in Ca
We have measured the ac-Stark shift of the 4s2 1S0 - 4s4p 3P1 line in 40Ca
for perturbing laser wavelengths between 780 nm and 1064 nm with a time domain
Ramsey-Borde atom interferometer. We found a zero crossing of the shift for the
mS = 0 - mP = 0 transition and \sigma polarized perturbation at 800.8(22) nm.
The data was analyzed by a model deriving the energy shift from known
transition wavelengths and strengths. To fit our data, we adjusted the Einstein
A coefficients of the 4s3d 3D - 4s4p 3P and 4s5s 3S - 4s4p 3P fine structure
multiplets. With these we can predict vanishing ac-Stark shifts for the 1S0 m =
0 - 3P1 m = 1 transition and \sigma- light at 983(12) nm and at 735.5(20) nm
for the transition to the 3P0 level.Comment: 8 pages, 5 figures, 2 table
Collisional losses, decoherence, and frequency shifts in optical lattice clocks with bosons
We have quantified collisional losses, decoherence and the collision shift in
a one-dimensional optical lattice clock with bosonic 88Sr. The lattice clock is
referenced to the highly forbidden transition 1S0 - 3P0 at 698 nm, which
becomes weakly allowed due to state mixing in a homogeneous magnetic field. We
were able to quantify three decoherence coefficients, which are due to
dephasing collisions, inelastic collisions between atoms in the upper and lower
clock state, and atoms in the upper clock state only. Based on the measured
coefficients, we determine the operation parameters at which a 1D-lattice clock
with 88Sr shows no degradation due to collisions on the relative accuracy level
of 10-16.Comment: 4 pages, 3 figure
Locking Local Oscillator Phase to the Atomic Phase via Weak Measurement
We propose a new method to reduce the frequency noise of a Local Oscillator
(LO) to the level of white phase noise by maintaining (not destroying by
projective measurement) the coherence of the ensemble pseudo-spin of atoms over
many measurement cycles. This scheme uses weak measurement to monitor the phase
in Ramsey method and repeat the cycle without initialization of phase and we
call, "atomic phase lock (APL)" in this paper. APL will achieve white phase
noise as long as the noise accumulated during dead time and the decoherence are
smaller than the measurement noise. A numerical simulation confirms that with
APL, Allan deviation is averaged down at a maximum rate that is proportional to
the inverse of total measurement time, tau^-1. In contrast, the current atomic
clocks that use projection measurement suppress the noise only down to the
level of white frequency, in which case Allan deviation scales as tau^-1/2.
Faraday rotation is one of the possible ways to realize weak measurement for
APL. We evaluate the strength of Faraday rotation with 171Yb+ ions trapped in a
linear rf-trap and discuss the performance of APL. The main source of the
decoherence is a spontaneous emission induced by the probe beam for Faraday
rotation measurement. One can repeat the Faraday rotation measurement until the
decoherence become comparable to the SNR of measurement. We estimate this
number of cycles to be ~100 cycles for a realistic experimental parameter.Comment: 18 pages, 7 figures, submitted to New Journal of Physic
Extreme non-linear response of ultra-narrow optical transitions in cavity QED for laser stabilization
We explore the potential of direct spectroscopy of ultra-narrow optical
transitions of atoms localized in an optical cavity. In contrast to
stabilization against a reference cavity, which is the approach currently used
for the most highly stabilized lasers, stabilization against an atomic
transition does not suffer from Brownian thermal noise. Spectroscopy of
ultra-narrow optical transitions in a cavity operates in a very highly
saturated regime in which non-linear effects such as bistability play an
important role. From the universal behavior of the Jaynes-Cummings model with
dissipation, we derive the fundamental limits for laser stabilization using
direct spectroscopy of ultra-narrow atomic lines. We find that with current
lattice clock experiments, laser linewidths of about 1 mHz can be achieved in
principle, and the ultimate limitations of this technique are at the 1 Hz
level.Comment: 5 pages, 4 figure
Magneto-Optical Trap for Thulium Atoms
Thulium atoms are trapped in a magneto-optical trap using a strong transition
at 410 nm with a small branching ratio. We trap up to atoms at
a temperature of 0.8(2) mK after deceleration in a 40 cm long Zeeman slower.
Optical leaks from the cooling cycle influence the lifetime of atoms in the MOT
which varies between 0.3 -1.5 s in our experiments. The lower limit for the
leaking rate from the upper cooling level is measured to be 22(6) s. The
repumping laser transferring the atomic population out of the F=3 hyperfine
ground-state sublevel gives a 30% increase for the lifetime and the number of
atoms in the trap.Comment: 4 pages, 6 figure
Writing Instructorsâ Intentional Integration of the Information Literacy Framework
This article presents an exploratory study that examines how 11 first-year writing instructorsâ conceptualizations of information literacy evolved over the course of their participation in an inquiry group co-developed and co-facilitated by the Librariesâ teaching faculty and the Director of Composition & Rhetoric at a public university in the United States. The authors developed a coding schema to identify the presence of information literacy-related themes and practices in pre- and post-program course syllabi and in reflective pieces submitted by instructors. The findings revealed that instructorsâ use and applications of the ACRL Framework increased after the program, showing greater personal engagement as evidenced by more preferential application of frames most relevant to their learning goals. Moreover, instructors integrated those frames more fully into their instructional practices. The authorsâ analysis of instructor-created artifacts provides a unique lens into disciplinary instructorsâ conceptualizations of and approaches to information literacy while examining the impact of one path for collaboration and scalability of information literacy integration within a curriculum
Doppler cooling and trapping on forbidden transitions
Ultracold atoms at temperatures close to the recoil limit have been achieved
by extending Doppler cooling to forbidden transitions. A cloud of ^40Ca atoms
has been cooled and trapped to a temperature as low as 6 \mu K by operating a
magneto-optical trap on the spin-forbidden intercombination transition.
Quenching the long-lived excited state with an additional laser enhanced the
scattering rate by a factor of 15, while a high selectivity in velocity was
preserved. With this method more than 10% of pre-cooled atoms from a standard
magneto-optical trap have been transferred to the ultracold trap. Monte-Carlo
simulations of the cooling process are in good agreement with the experiments
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