Telephone: (507) 646-3619
Office: Science Center 118
I have been a member of the St. Olaf faculty since 1979. My research interests are in atomic and molecular physics, and include work on radiofrequency hyperfine spectroscopy (in collaboration with the St. Olaf Molbeam group headed by James Cederberg ), measurement of atomic transition probabilities and excited state lifetimes, multiphoton laser spectroscopy, and atomic collisions. Here is my CV.
Courses: In the past few years I have been teaching Introductory Astronomy (Phys. 112), the Musical Acoustics Interim (Phys. 252), Principles of Physics II (Phys. 125), Quantum Mechanics (Phys. 376) and the Advanced Laboratory Course for Seniors (Phys. 386). I enjoy developing computer-based resources as aids for learning in these courses. Here are a few sample animations, all in Windows .avi format:
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Astronomy
Daily path of the Sun over the course of 1 year for an observer near Northfield, Minnesota (latitude 44.5 deg. N) (about 15 MB)
This animation plots the hour-by-hour location of the sun on successive days of the year (beginning with the vernal equinox) relative to the horizon plane of an observer near Northfield. The distorted figure-8 pattern (analemma) traced out by the daily variation of the sun's position at noon is highlighted - a consequence of the combined effects of the earth's tilt and variation of orbital speed. From this animation one can also see interesting patterns in the times of sunrise and sunset by thinking of the "circle of suns" plotted in the figure as markers on a 24 hour clock and noticing where the circle intersects the horizon plane on a given day of the year. This circle not only rises and falls with the seasons - producing the familiar increase and decrease in hours of daylight - but also rotates back and forth slowly as the noon sun moves around the analemma. Near the summer and winter solstices (sun at the top or bottom of the analemma) the circle's motion is almost entirely rotational - clockwise as you look at the screen - meaning that sunrise and sunset both shift toward later times of day for a brief period (roughly June 15 - 26 in summer, Dec. 9 - Jan 2 in winter) before resuming their more "normal" pattern of moving in opposition.
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Acoustics
Normal modes of vibration of an idealized two-dimensional membrane (about 6 MB each):
(1) Fundamental (2) Mode with one nodal diameter (3) Mode with one nodal circle (4) Mode with one nodal diameter and one nodal circle
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Quantum Mechanics
Motion of free particle wave packets (about 2 MB each):
In this pair of animations, the free particle is represented by a Gaussian-distributed linear combination of momenta in accordance with the uncertainty principle. The peak momemtum corresponds to a kinetic energy of 60 units. Classically speaking, the particle would need a kinetic energy of 200 units to be able to get over the barriers, but in quantum mechanics the wave-like aspect of the particle yields a non-zero probability for particles of lower energy to cross the barrier (and in the second case, to get trapped between the barriers).
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