1,160 research outputs found
Observation of Heteronuclear Feshbach Molecules from a Rb - Rb gas
We report on the observation of ultracold heteronuclear Feshbach molecules.
Starting with a Rb BEC and a cold atomic gas of Rb, we utilize
previously unobserved interspecies Feshbach resonances to create up to 25,000
molecules. Even though the Rb gas is non-degenerate we observe a large
molecular conversion efficiency due to the presence of a quantum degenerate
Rb gas; this represents a key feature of our system. We compare the
molecule creation at two different Feshbach resonances with different
magnetic-field widths. The two Feshbach resonances are located at
G and G. We also directly measure the small
binding energy of the molecules through resonant magnetic-field association.Comment: v2 - minor change
Spontaneous Dissociation of 85Rb Feshbach Molecules
The spontaneous dissociation of 85Rb dimers in the highest lying vibrational
level has been observed in the vicinity of the Feshbach resonance which was
used to produce them. The molecular lifetime shows a strong dependence on
magnetic field, varying by three orders of magnitude between 155.5 G and 162.2
G. Our measurements are in good agreement with theoretical predictions in which
molecular dissociation is driven by inelastic spin relaxation. Molecule
lifetimes of tens of milliseconds can be achieved close to resonance.Comment: 4 pages, 3 figure
Studying a dual-species BEC with tunable interactions
We report on the observation of controllable spatial separation in a
dual-species Bose-Einstein condensate (BEC) with Rb and Rb.
Interparticle interactions between the different components can change the
miscibility of the two quantum fluids. In our experiments, we clearly observe
the immiscible nature of the two simultaneously Bose-condensed species via
their spatial separation. Furthermore the Rb Feshbach resonance near 155
G is used to change them between miscible and immiscible by tuning the
Rb scattering length. Our apparatus is also able to create Rb
condensates with up to atoms which represents a significant
improvement over previous work
Reforming a large lecture modern physics course for engineering majors using a PER-based design
We have reformed a large lecture modern physics course for engineering majors
by radically changing both the content and the learning techniques implemented
in lecture and homework. Traditionally this course has been taught in a manner
similar to the equivalent course for physics majors, focusing on mathematical
solutions of abstract problems. Based on interviews with physics and
engineering professors, we developed a syllabus and learning goals focused on
content that was more useful to our actual student population: engineering
majors. The content of this course emphasized reasoning development, model
building, and connections to real world applications. In addition we
implemented a variety of PER-based learning techniques, including peer
instruction, collaborative homework sessions, and interactive simulations. We
have assessed the effectiveness of reforms in this course using pre/post
surveys on both content and beliefs. We have found significant improvements in
both content knowledge and beliefs compared with the same course before
implementing these reforms and a corresponding course for physics majors.Comment: To be published in the Proceedings of the Physics Education Research
Conference 200
Chemistry vs. Physics: A Comparison of How Biology Majors View Each Discipline
A student's beliefs about science and learning science may be more or less sophisticated depending on the specific science discipline. In this study, we used the physics and chemistry versions of the Colorado Learning Attitudes about Science Survey (CLASS) to measure student beliefs in the large, introductory physics and chemistry courses, respectively. We compare how biology majors -- generally required to take both of the courses -- view these two disciplines. We find that these students' beliefs are more sophisticated about physics (more like the experts in that discipline) than they are about chemistry. At the start of the term, the average % Overall Favorable score on the CLASS is 59% in physics and 53% in chemistry. The students' responses are statistically more expert-like in physics than in chemistry on 10 statements (P lesser-than-or-equal-to 0.01), indicating that these students think chemistry is more about memorizing disconnected pieces of information and sample problems, and has less to do with the real world. In addition, these students' view of chemistry degraded over the course of the term. Their favorable scores shifted -5.7% and -13.5% in 'Overall' and the 'Real World Connection' category, respectively; in the physics course, which used a variety of research-based teaching practices, these scores shifted 0.0% and +0.3%, respectively. The chemistry shifts are comparable to those previously observed in traditional introductory physics courses
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Observation of Heteronuclear Feshbach Molecules from a 85Rb – 87Rb gas
We report on the observation of ultracold heteronuclear Feshbach molecules. Starting with a 87Rb Bose-Einstein condensate and a cold atomic gas of 85Rb, we utilize previously unobserved interspecies Feshbach resonances to create up to 25,000 molecules. Even though the 85Rb gas is nondegenerate, we observe a large molecular conversion efficiency due to the presence of a quantum degenerate 87Rb gas; this represents a key feature of our system. We compare the molecule creation at two different Feshbach resonances with different magnetic-field widths. The two Feshbach resonances are located at 265.44±0.15   G and 372.4±1.3  G. We also directly measure the small binding energy of the molecules through resonant magnetic-field association
Developing and Researching PhET simulations for Teaching Quantum Mechanics
Quantum mechanics is difficult to learn because it is counterintuitive, hard
to visualize, mathematically challenging, and abstract. The Physics Education
Technology (PhET) Project, known for its interactive computer simulations for
teaching and learning physics, now includes 18 simulations on quantum mechanics
designed to improve learning of this difficult subject. Our simulations include
several key features to help students build mental models and intuitions about
quantum mechanics: visual representations of abstract concepts and microscopic
processes that cannot be directly observed, interactive environments that
directly couple students' actions to animations, connections to everyday life,
and efficient calculations so students can focus on the concepts rather than
the math. Like all PhET simulations, these are developed using the results of
education research and feedback from educators, and are tested in student
interviews and classroom studies. This article provides an overview of the PhET
quantum simulations and their development. We also describe research
demonstrating their effectiveness and share some insights about student
thinking that we have gained from our research on quantum simulations.Comment: accepted by American Journal of Physics; v2 includes an additional
study, more explanation of research behind claims, clearer wording, and more
reference
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