31 research outputs found
Enhanced molecular yield from a cryogenic buffer gas beam source via excited state chemistry
We use narrow-band laser excitation of Yb atoms to substantially enhance the brightness of a cold beam of YbOH, a polyatomic molecule with high sensitivity to physics beyond the standard model (BSM). By exciting atomic Yb to the metastable ³P₁ state in a cryogenic environment, we significantly increase the chemical reaction cross-section for collisions of Yb with reactants. We characterize the dependence of the enhancement on the properties of the laser light, and study the final state distribution of the YbOH products. The resulting bright, cold YbOH beam can be used to increase the statistical sensitivity in searches for new physics utilizing YbOH, such as electron electric dipole moment and nuclear magnetic quadrupole moment experiments. We also perform new quantum chemical calculations that confirm the enhanced reactivity observed in our experiment and compare reaction pathways of Yb(³P) with the reactants H₂O and H₂O₂. More generally, our work presents a broad approach for improving experiments that use cryogenic molecular beams for laser cooling and precision measurement searches of BSM physics
Enhanced molecular yield from a cryogenic buffer gas beam source via excited state chemistry
We use narrow-band laser excitation of Yb atoms to substantially enhance the brightness of a cold beam of YbOH, a polyatomic molecule with high sensitivity to physics beyond the standard model (BSM). By exciting atomic Yb to the metastable ³P₁ state in a cryogenic environment, we significantly increase the chemical reaction cross-section for collisions of Yb with reactants. We characterize the dependence of the enhancement on the properties of the laser light, and study the final state distribution of the YbOH products. The resulting bright, cold YbOH beam can be used to increase the statistical sensitivity in searches for new physics utilizing YbOH, such as electron electric dipole moment and nuclear magnetic quadrupole moment experiments. We also perform new quantum chemical calculations that confirm the enhanced reactivity observed in our experiment and compare reaction pathways of Yb(³P) with the reactants H₂O and H₂O₂. More generally, our work presents a broad approach for improving experiments that use cryogenic molecular beams for laser cooling and precision measurement searches of BSM physics
Cold heteromolecular dipolar collisions
We present the first experimental observation of cold collisions between two
different species of neutral polar molecules, each prepared in a single
internal quantum state. Combining for the first time the techniques of Stark
deceleration, magnetic trapping, and cryogenic buffer gas cooling allows the
enhancement of molecular interaction time by 10. This has enabled an
absolute measurement of the total trap loss cross sections between OH and
ND at a mean collision energy of 3.6 cm (5 K). Due to the dipolar
interaction, the total cross section increases upon application of an external
polarizing electric field. Cross sections computed from \emph{ab initio}
potential energy surfaces are in excellent agreement with the measured value at
zero external electric field. The theory presented here represents the first
such analysis of collisions between a radical and a closed-shell
polyatomic molecule.Comment: 7 pages, 5 figure
Collision-induced C_60 rovibrational relaxation probed by state-resolved nonlinear spectroscopy
Quantum state-resolved spectroscopy was recently achieved for C60 molecules
when cooled by buffer gas collisions and probed with a midinfrared frequency
comb. This rovibrational quantum state resolution for the largest molecule on
record is facilitated by the remarkable symmetry and rigidity of C60, which
also present new opportunities and challenges to explore energy transfer
between quantum states in this many-atom system. Here we combine state-specific
optical pumping, buffer gas collisions, and ultrasensitive intracavity
nonlinear spectroscopy to initiate and probe the rotation-vibration energy
transfer and relaxation. This approach provides the first detailed
characterization of C60 collisional energy transfer for a variety of collision
partners, and determines the rotational and vibrational inelastic collision
cross sections. These results compare well with our theoretical modeling of the
collisions, and establish a route towards quantum state control of a new class
of unprecedentedly large molecules
SOSORT 2012 consensus paper: reducing x-ray exposure in pediatric patients with scoliosis
This 2012 Consensus paper reviews the literature on side effects of x-ray exposure in the pediatric population as it relates to scoliosis evaluation and treatment. Alternative methods of spinal assessment and imaging are reviewed, and strategies for reducing the number of radiographs are developed. Using the Delphi technique, SOSORT members developed consensus statements that describe how often radiographs should be taken in each of the pediatric and adolescent sub-populations
PERFORMANCE EVALUATION OF ROUNDABOUTS USING A MICROSCOPIC SIMULATION MODEL
Contemporary planning of the road network in cities assumes the use of transport models. The microscopic model allows provision of information and decision-making regarding, for example, emissions, traffic organisation, geometrics of the intersection and traffic control system. This article describes the development of comprehensive methodology applied for carrying out the research related to the design of geometrical parameters of the roundabout. The methodology involves developing instructions for preparing solutions for performance evaluations of roundabouts using a microscopic simulation model with the VISSIM software. The application of the developed methodology was prepared on the case study of the roundabout in Gdańsk. The results of the prepared case study were discussed