Exploring the contributions of self-efficacy and test anxiety to gender differences in assessments

The observed performance difference between women and men on assessments in physics---the "gender gap"---is a significant and persistent inequity which has broad implications for the participation of women in physics. Research also shows that gender-based inequities extend to affective measures, such as self-efficacy. In this exploratory study, we report on gender disparities in self-efficacy and test anxiety and their relationship to assessment scores in our active-learning introductory physics course. Overall, gender-based differences in favour of men are observed in all our measures, with women having lower scores on measures associated with success (self-efficacy and assessment scores) and a higher score on a possibly detrimental affective factor (test anxiety). Using a multiple regression model-selection process to explore which measures may explain end-of-course Force Concept Inventory (FCI) and final exam scores, we find that the best fitting models include FCI pretest and self-efficacy as predictors, but do not include test anxiety.Comment: Accepted to the 2020 Physics Education Research Conference Proceeding

Timing and Interstellar Scattering of Thirty-five Distant Pulsars Discovered in the PALFA Survey

We have made extensive observations of 35 distant slow (non-recycled) pulsars discovered in the ongoing Arecibo PALFA pulsar survey. Timing observations of these pulsars over several years at Arecibo Observatory and Jodrell Bank Observatory have yielded high-precision positions and measurements of rotation properties. Despite being a relatively distant population, these pulsars have properties that mirror those of the previously known pulsar population. Many of the sources exhibit timing noise, and one underwent a small glitch. We have used multifrequency data to measure the interstellar scattering properties of these pulsars. We find scattering to be higher than predicted along some lines of sight, particularly in the Cygnus region. Finally, we present XMM-Newton and Chandra observations of the youngest and most energetic of the pulsars, J1856+0245, which has previously been associated with the GeV-TeV pulsar wind nebula HESS J1857+026

Dipole-Dipole Interaction between Rubidium Rydberg Atoms

Ultracold Rydberg atoms in a static electric field can exchange energy via the dipole-dipole interaction. The Stark effect shifts the energy levels of the atoms which tunes the energy exchange into resonance at specific values of the electric field (Forster resonances). We excite rubidium atoms to Rydberg states by focusing either a 480 nm beam from a tunable dye laser or a pair of diode lasers into a magneto-optical trap. The trap lies at the center of a configuration of electrodes. We scan the electric field by controlling the voltage on the electrodes while measuring the fraction of atoms that interact. Dipole-dipole interaction spectra are presented for initially excited rubidium nd states for n = 31 to 46 and for four different pairs of initially excited rubidium ns states. We also present the dipole-dipole interaction spectra for individual rubidium 32d (j, m(j)) fine structure levels that have been selectively excited. The data are compared to calculated spectra

Dipole-Dipole Interaction Between Rubidium Rydberg Atoms

Ultracold Rydberg atoms in a static electric field can exchange energy via the dipole-dipole interaction. The Stark effect shifts the energy levels of the atoms which tunes the energy exchange into resonance at specific values of the electric field (F¨orster resonances). We excite rubidium atoms to Rydberg states by focusing either a 480 nm beam from a tunable dye laser or a pair of diode lasers into a magneto-optical trap. The trap lies at the center of a configuration of electrodes. We scan the electric field by controlling the voltage on the electrodes while measuring the fraction of atoms that interact. Dipole-dipole interaction spectra are presented for initially excited rubidium nd states for n = 31 to 46 and for four different pairs of initially excited rubidium ns states. We also present the dipole-dipole interaction spectra for individual rubidium 32d (j,mj ) fine structure levels that have been selectively excited. The data are compared to calculated spectra

High resolution two-photon spectroscopy of ¹²⁹Xe for precision optical magnetometry

This dissertation presents high precision two-photon xenon spectroscopy of the 5p₅(²P₃/₂)6p²[3/2]₂ ⟵5p⁶(¹S₀) transition. Specific attention is paid to the F = 3/2 hyperfine level of ¹²⁹Xe, motivated by the new experiment at TRIUMF to measure the electric dipole moment of the neutron. A non-zero value of the nEDM would partially confirm the existence of the baryon asymmetry in the universe as predicted by theories beyond the standard model. To achieve this measurement, ¹²⁹Xe is proposed for use in a cohabiting ¹⁹⁹Hg/¹²⁹Xe optical comagnetometer. To date, no laser system has existed to probe the specific xenon transition required for this measurement. We developed a novel continuous-wave 252.4 nm ultra-violet (UV) laser system with the power and precision to selectively probe the hyperfine levels of ¹²⁹Xe. Using this laser, we observed the first high resolution two-photon transition spectrum of xenon, which is comprised of ten transition peaks across the six most abundant isotopes, including the hyperfine levels of the ¹²⁹Xe and ¹³¹Xe. Detailed analysis of this spectrum revealed the hyperfine constants of the 5p₅(²P₃/₂)6p²[3/2]₂ excited state and other constants relating to the isotope shift. Furthermore, we describe initial observations into the pressure dependencies of the spectral lineshape from 15–980 mTorr. The ¹²⁹Xe pressure in the nEDM experiment is limited to 3 mTorr, making it essential to characterize the xenon signal at low pressures to maximize comagnetometer sensitivity. Intriguingly, our results suggest that ¹²⁹Xe qualitatively exhibits nonlinear pressure broadening at low pressure (<200 mTorr) - a phenomenon reminiscent of helium, neon and krypton. However, further investigation is required to fully characterize the pressure broadening effects in ¹²⁹Xe. Overall, these results define the expected signal lineshape and relative transition frequency to the F = 3/2 hyperfine level of ¹²⁹Xe for precision laser tuning. Collectively, this work contributes to optical magnetometry in nEDM experiments, as well as to precision spectroscopy and theories of atom-atom interactions.Science, Faculty ofPhysics and Astronomy, Department ofGraduat

The adventures of Nikita and Casper : high power ultraviolet lasers for precision spectroscopy

The Optically Pumped Semiconductor Laser (OPSL) offers several advantages as a laser source for precision spectroscopy. The semiconductor gain bandwidth allows an OPSL to run continuous wave (CW) between 920 - 1154 nm and with a free running linewidth 500 kHz. High powers have been observed in OPSL, as high as 70 W. Paired with doubling crystals the wavelength range can be extended down to the ultraviolet(UV) with high power. This research presents an OPSL operating at 972 nm at 1.7 W sequentially doubled down twice to a wavelength of 243 nm at 150 mW. The linewidth is reduced by locking one OPSL to a Fabry-Poret stabilization cavity and then the relative linewidth was measured between two OPSL's locked together. The linewidth is determined to be 87 kHz, dominated mostly by technical noise. This laser is set to be used for cryogenic hydrogen spectroscopy and precision measurements of the Lamor precessional frequency of ¹²⁹Xe when it is used as a comagnetometer for measuring the electrical dipole moment (EDM) of the neutron.Science, Faculty ofPhysics and Astronomy, Department ofGraduat