Physics Department
Professor
Ph.D., University of Connecticut
Fields: Experimental condensed matter physics — properties of magnetic materials; materials analysis using X-ray diffraction, Mössbauer spectroscopy, and nuclear magnetic resonance; solid state physics and NMR theory.
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Email: dyang@holycross.edu
Office Phone: 508-793-2463
FAX: 508-793-3367
Office: Haberlin 110
Lab: Haberlin 121
PO Box:143A
Office Hours: Wed. 10am -11am, noon - 3pm, and by appointment
Research
My research has been in the experimental investigation of solid state materials that contain nuclear magnetic moments. The main experimental methods are nuclear magnetic resonance (NMR), recoil-less gamma ray absorption spectroscopy (Mössbauer spectroscopy), x-ray diffraction, bulk magnetization measurements (hysteresis, Meissner effect), thermal measurements (heat capacity, calorimetry), and computer simulation/modeling. The investigated materials include amorphous alloys, high TC superconductors, rare-earth permanent magnets, membranes containing drug molecules, and Fe-based nanocrystalline alloys. Research results have been reported at international conferences and regional seminars, and published in scientific journals, research monographs, and a book Mössbauer Effect in Lattice Dynamics by Wiley.
My research laboratory on the Holy Cross campus has a Mössbauer spectrometer, in which a gamma ray source, cobalt-57 in a sealed rhodium matrix, is mechanically modulated by an ultra-linear constant-acceleration driving motor with a typical maximum velocity of 12 mm/s. A laser in a Michelson interferometer is used to monitor the velocity profile. Sample temperature may be continuously regulated down to cryogenic temperatures of about 15 K or raised to high temperatures up to 700 K. Proportional detection of the transmitted gamma rays is synchronized with the source motion, and the data are registered in a multi-channel analyzer in a computer. Mössbauer spectra are recorded and analyzed to provide information on the atomic and electronic structures of the material. Techniques such as high vacuum, high pressure helium gas, cryogenic temperature, high voltage, and digital electronics are used, but each component of the apparatus is made accessible, suitable for engaging undergraduate students. So far, there have been five students who have worked in the laboratory during two summer periods and three regular semesters. The Mössbauer spectrometer has also been used for teaching in the Experimental Solid State Physics course.
Courses
Courses in Spring 2018:
- Electronics (PHYS 234)
An introduction to analog and digital electronics using discrete semiconductor components and integrated circuit chips. Theory and methodology are discussed in terms of Kirchhoff 's laws applied to DC and AC circuits, the characteristics of diodes and transistors, and the properties of IC chips. This course also explores the physics of semiconductors, behaviors of diodes and transistors, and their circuit applications including rectifiers, regulators, amplifiers, oscillators, and feedback systems, specifically operational amplifier circuits. The digital circuitry focuses on logic gates, comparators, binary number counting and processing, and programmable microcontrollers. - Electronics Laboratory (PHYS 236)
This is the advanced laboratory course accompanying Physics 234. It is designed to allow students to explore various analog and digital circuits. Professional equipment including digital oscilloscopes, prototyping boards, digital multimeters are used in the design, construction, and testing of AC and DC circuits, including low- and high-pass filters, resonance circuits, rectifiers, transistor amplifiers with feedback, oscillators, 555-timer circuits, operational amplifiers, transistor-transistor logic (TTL) integrated circuits, logic gates, flip-flops, binary counters, binary-coded decimal representations and displays, binary computations, and a programmable microcontroller.
Other Courses:
- Intro Physics 1
First part of the two-semester General Physics sequence covering linear, rotational, oscillatory motions with accociated concepts of acceleration, force, torque, energy, momentum, pressure, etc. - Intro Physics 2
Second part of two-semester General Physics sequence covering electricity, magnetism, optics, and modern physics. Laboratory exercises are integrated into the lectures. (Course materials online on Moodle at https://learning.holycross.edu/hcmoodle/) - Methods of Physics
Mathematical methods and applications in physics: differential equations, vector calculus, matrices, complex variables, etc. - Modern Physics Laboratory
Quantum, relativity, and nuclear experiments. - Electromagnetic Theory
Comprehensive theory of static and dynamic electromagnetic phenomena, including Maxwell's equations and special theory of relativity. - Optics
Lectures on theories of how light is emitted, how light travels through media, and how light interacts with matter. Including geometric optics and wave optics. - Optics Laboratory
Specialized laboratory for physics majors (geometric and physical optics investigated using lasers). - Thermal Physics
Thermodynamics and Statistical Mechanics for physics majors (thermodynamics laws, equation of state, energy and enthopy, Probability and partition functions). - Experimental Solid State Physics
A combined theoretical and experimental course on solid state physics, including crystallography, electronic energy bands, magnetic materials, Mössbauer spectroscopy. - Light, Colors and Vision
For non-science majors; this is a qualitative (non-mathematical) course on the nature and myth of light and color, and the mechanism of vision. - Colors in Nature and the Nature of Colors
Honors Seminar, combining science, technology, history, art, literature, photography, and film.
Publications
2009 IEEE Transactions on Magnetics, 45, 3901- 3904 (2009) PDF
Review Article in Encyclopedia of Applied Spectroscopy
(ISBN 978-3-527-40773-6) pp. 51-85. (2009).
2011 Biochimica et Biophysica Acta, 1808, 2095-2101 (2011). PDF
2013 The AAPS Journal, 15, 477-482 (2013). PDF
2015 Chemical Biology and Drug Design, 85, 534-540 (2015). PDF
2016 Biochimica et Biophysica Acta, 1858, 344-353 (2016). PDF