*86%*:**Student difficulties with finding the corrections to the energy spectrum of the hydrogen atom for the strong and weak field Zeeman effects using degenerate perturbation theory***52%*:**Student difficulties with the corrections to the energy spectrum of the hydrogen atom for the intermediate field Zeeman effect***31%*:**Developing and evaluating an interactive tutorial on degenerate perturbation theory***25%*:**Investigating Student Understanding of Perturbation Theory and the Inner Products of Functions***24%*:**Using student-generated content to engage students in upper-division quantum mechanics***24%*:**Using Eye Tracking to Differentiate Student Difficulties Reasoning with Data***23%*:**Investigating student understanding of basic quantum mechanics in the context of time-dependent perturbation theory***22%*:**Using two models in optics: Students' difficulties and suggestions for teaching***22%*:**Investigating Student Difficulties with Dirac Notation***22%*:**Student understanding of potential, wavefunctions and the Jacobian in hydrogen in graduate-level quantum mechanics***22%*:**Model-based inquiry vs. Traditional computer simulation-based instruction: Which can better help students construct the quantum-mechanical model of an atom?***21%*:**Addressing Students' Difficulties in Understanding Two Different Expressions of Gravitational Potential Energy (I): mgh & -GMm/r***21%*:**Exploring Student Understanding of Atoms and Radiation with the Atom Builder Simulator***21%*:**Teachers' explanations of student difficulties with gravitational potential energy***21%*:**Using multiple survey questions about energy to uncover elements of middle school student reasoning***21%*:**Teaching gravitational potential energy: Student interaction with surface manipulatives***20%*:**Model analysis of fine structures of student models: An example with Newton's third law***19%*:**Relationship between students' conceptual knowledge and study strategies-part I: student learning in physics***19%*:**Students' Understanding of the Special Theory of Relativity and Design for a Guided Visit to a Science Museum**