Prof. Paul Oxley, Physics, College of the Holy Cross Office: Haberlin 107 ; Lab: Haberlin 127; 508-793-2473 poxley@holycross.edu

Students	Publications	Previous Research

Description of Current Research

In my lab undergraduate students and I primarily perform experiments using highly-excited atoms, called Rydberg atoms.  The long term goal of our experiments is to study collisions between Rydberg atoms and ions.  We aim to use these studies to improve physicists’ understanding of the role Rydberg atoms play in determining the physical properties of plasmas.  A plasma is a collection of ions, electrons, and often Rydberg atoms and 99% of the visible universe is in a plasma state.  Plasmas occur in the interstellar medium, in planetary atmospheres, in fusion reactors designed to produce cheap, clean electrical power, and in gas discharges such as fluorescent lamps. In the lab we create Rydberg lithium atoms by sequential laser excitation using up to four diode lasers.  The lithium atoms are produced in a home-built oven where solid lithium is heated in vacuum to 500ºC – hot enough for a beam of atoms to emerge from the oven and then be laser excited.  We have made precise measurements of the atomic structure of the Rydberg lithium atoms and are assembling an ion source to provide a beam of ions which we will collide with the atoms. We also perform experiments in the field of applied magnetism. We have measured the magnetic properties of different types of magnetic stainless steel at room and at cryogenic temperature. We have also designed, constructed, and tested an electronic circuit to automatically magnetize and demagnetize magnetic materials Below are some pictures and descriptions of the work we have done.  Enjoy.

Energy Levels of Lithium and lasers needed to excite to the 10p Rydberg state	Simplified version of the setup to combine the three lasers used to excite Lithium to the 10p state	Schematic of how the three lasers are frequency stabilized
Photo of one of the laser diodes	Photo of the lithium oven	Optics used to put the 670nm and 813nm lasers on the same optical path. Lasers are inside the silver boxes
More optics to combine and to monitor the laser wavelength and frequency spectrum	View of the apparatus used to excite lithium with all three lasers	Fluorescence at 670nm induced by laser on resonance with the first transition. The Li beam is coming out of the plane of the page.
Detected 2p - 2s fluorescence from the first laser transition	Detected 3s - 2p fluorescence from the first laser transition	Fluorescence from the final laser excitation (10p-2s ground state)
View of the lab	View of the lab in the dark, when experiment is running	The nearly assembled ion source and vacuum system
Close up of the ion source	Electronics used to run the ion source, a full 6 feet tall rack	Experimetal setup used to study the magnetic properties of stainless steels. Front left are the demagnetization electronics, front right magnetizing coil with steel sample inside
The magnetizing coil which is used to apply a magnetic field to the stainless steel sample	Stainless steel sample with field coil attached to measure the magnetic field	Close up of flux coil wound on steel sample and field coil next to steel sample
Close up view of electronics used to demagnetize magnetis samples