A Partnership\u27s Effort to Improve the Teaching of K-12 Mathematics in Rapid City, South Dakota

Over the span of ten years, a National Science Foundation‐funded partnership effort has collected and analyzed multiple forms of evidence, both direct and indirect, about improved teaching of mathematics within Rapid City Area Schools. This article describes the project\u27s impact on K‐12 teaching and factors contributing to that impact. The authors argue that improvements in teaching are attributable largely to a robust infrastructure established to support teacher growth. Direct evidence includes classroom observations conducted by the project\u27s external evaluation team. Indirect evidence exists in the form of data on student outcomes: achievement on the state\u27s multiple‐choice accountability measure and achievement on project‐administered performance assessments

Deep Underground Science and Engineering Laboratory - Preliminary Design Report

The DUSEL Project has produced the Preliminary Design of the Deep Underground Science and Engineering Laboratory (DUSEL) at the rehabilitated former Homestake mine in South Dakota. The Facility design calls for, on the surface, two new buildings - one a visitor and education center, the other an experiment assembly hall - and multiple repurposed existing buildings. To support underground research activities, the design includes two laboratory modules and additional spaces at a level 4,850 feet underground for physics, biology, engineering, and Earth science experiments. On the same level, the design includes a Department of Energy-shepherded Large Cavity supporting the Long Baseline Neutrino Experiment. At the 7,400-feet level, the design incorporates one laboratory module and additional spaces for physics and Earth science efforts. With input from some 25 science and engineering collaborations, the Project has designed critical experimental space and infrastructure needs, including space for a suite of multidisciplinary experiments in a laboratory whose projected life span is at least 30 years. From these experiments, a critical suite of experiments is outlined, whose construction will be funded along with the facility. The Facility design permits expansion and evolution, as may be driven by future science requirements, and enables participation by other agencies. The design leverages South Dakota's substantial investment in facility infrastructure, risk retirement, and operation of its Sanford Laboratory at Homestake. The Project is planning education and outreach programs, and has initiated efforts to establish regional partnerships with underserved populations - regional American Indian and rural populations

Frustrated tunnelling ionization during strong-field fragmentation of D3+

We reveal surprisingly high kinetic energy release in the intense-field fragmentation of D[subscript 3][superscript +] to D[superscript +] + D[superscript +] + D with 10[superscript 16]Wcm[superscript −2], 790 nm, 40 fs (and 7 fs) laser pulses. This feature strongly mimics the behaviour of the D[superscript +] + D[superscript +] + D[superscript +] channel. From the experimental evidence, we conclude that the origin of the feature is due to frustrated tunnelling ionization, the first observation of this mechanism in a polyatomic system. Furthermore, we unravel evidence of frustrated tunnelling ionization in dissociation, both two-body breakup to D + D[subscript 2][superscript +] and D[superscript +] + D[subscript 2], and three-body breakup to D[superscript +] + D + D

Elucidating isotopic effects in intense ultrafast laser-driven D2H+ fragmentation

The triatomic hydrogen molecular ion is instrumental as a benchmark toward understanding the strong-field dynamics of polyatomic molecules. Using a crossed-beams coincidence three-dimensional momentum imaging method, we demonstrate clear isotopic effects in the fragmentation of D[subscript 2]H[superscript +] induced by 7 fs (40 fs), 790 nm laser pulses at an intensity of 10[superscript 16] W/cm² (5×10[superscript 15] W/cm²). Our experiment uniquely separates all fragmentation channels and provides kinematically complete information for the nuclear fragments. For example, we show that for dissociative ionization of D[subscript 2]H[superscript +] there is a large difference in branching ratios of the two-body channels, namely, H[superscript +]+D[superscript +][subscript 2] dominates D[superscript +]+HD[superscript +], whereas there is minimal difference in branching ratios between the dissociation channels H[superscript +]+D[subscript 2] and D[superscript +]+HD

Nonunique and nonuniform mapping in few-body Coulomb-explosion imaging

Citation: Sayler, A. M., Eckner, E., McKenna, J., Esry, B. D., Carnes, K. D., Ben-Itzhak, I., & Paulus, G. G. (2018). Nonunique and nonuniform mapping in few-body Coulomb-explosion imaging. Physical Review A, 97(3), 033412. https://doi.org/10.1103/PhysRevA.97.033412Much of our knowledge of molecular geometry and interaction dynamics comes from indirect measurements of the molecular fragments following breakup. This technique—Coulomb-explosion imaging (CEI), i.e., determining the initial molecular configuration of a system from the momenta of the resulting fragments using knowledge of the particle interactions—is one of the fundamental tools of molecular physics. Moreover, CEI has been a staple of molecular studies for decades. Here we show that one often cannot assign a unique initial configuration to the few-body breakup of a polyatomic molecule given the measurement of the resulting fragments' momenta. Specifically, multiple initial configurations can result in identical momenta for a molecule breaking into three or more parts. Further, the nonunique and nonuniform mapping from the initial configuration to the measured momenta also significantly complicates the determination of molecular alignment at the time of breakup

Bond rearrangement during Coulomb explosion of water molecules

Bond rearrangement, namely the dissociation of water ions into H2++O(q−1)+ (q=1–4) following fast ion-impact ionization, unexpectedly occurs following multiple ionization of water in spite of the presumably fast “Coulomb explosion” of the transient molecular ion. Furthermore, the branching ratio of bond rearrangement is found to be nearly equal for each level of ionization, q. In addition, formation of H2+ is more than twice as likely to occur from the lighter water isotopologue H2O+ than D2+ from D2O+. These findings are consistent with the ground state dissociation mechanism in which a fast projection of the ground state nuclear wave function onto the vibrational continuum of the cation potential energy surface is sometimes followed by H2+ formation

Attosecond tracing of correlated electron-emission in non-sequential double ionization

Despite their broad implications for phenomena such as molecular bonding or chemical reactions, our knowledge of multi-electron dynamics is limited and their theoretical modelling remains a most difficult task. From the experimental side, it is highly desirable to study the dynamical evolution and interaction of the electrons over the relevant timescales, which extend into the attosecond regime. Here we use near-single-cycle laser pulses with well-defined electric field evolution to confine the double ionization of argon atoms to a single laser cycle. The measured two-electron momentum spectra, which substantially differ from spectra recorded in all previous experiments using longer pulses, allow us to trace the correlated emission of the two electrons on sub-femtosecond timescales. The experimental results, which are discussed in terms of a semiclassical model, provide strong constraints for the development of theories and lead us to revise common assumptions about the mechanism that governs double ionization

Single-shot carrier-envelope-phase-tagged ion-momentum imaging of nonsequential double ionization of argon in intense 4-fs laser fields

Journals published by the American Physical Society can be found at http://publish.aps.org