Erica L. Snow
Department of Physics
SUNY College at Fredonia
- Colorado State University, Ph.D. 2006
- Colorado State University, MS, 2003
- Grove City College, BS, 2001
- Experimental Atomic, Molecular, and Optical Physics
- Laser and microwave spectroscopy
- Rydberg atoms and molecules
Research Description: (under construction)
When an electron is highly excited but still weakly bound to a positive ion core it is called a Rydberg state. More specifically, high-angular-momentum (high-L) Rydberg states have nearly circular orbits at long distances. Since the excited electron essentially does not penetrate the ion core the system can be described nearly as would a hydrogen atom, which has an exact solution. It is this difference from hydrogenic that leads to the determination of properties of the positive ion core such as the polarizabilities and permanent multipole moments. As the field of atomic and molecular physics moves to cold and ultracold studies, the understanding of long-range interactions plays a significant role. Theoretical models and calculations don’t necessarily have a smooth transition between short and long-range regions. Very precise measurements are required to provide necessary benchmarks to check and in many cases instigate improved theory. The polarizability of an atom, molecule, or ion is a property which can be precisely measured and also calculated using the same theoretical values used in other physical studies. The polarizability is directly correlated to other properties such as lifetimes, dielectric constants, and index of refraction but, can be measured with more precision by study of high-angular momentum Rydberg states.
There are few direct measurements of H2+ because of the lack of bound electronic excited states. However, an excited electron, bound to an ion core, in a non-penetrating nearly circular orbit can act as a very sensitive probe to investigate electric and magnetic properties of the ion core. High angular momentum Rydberg states meet this criterion and, therefore, precise studies of these spectra afford the opportunity to detect long-range properties of the ion. The basic model in molecular physics, H2+, has been studied extensively by theorists, but there are comparatively few precise experimental measurements. The need for accurate models beyond the adiabatic approximation is increasing, and several theoretical approaches have been developed. This study will provide an excellent avenue to test the accuracy of the theoretical models. If successful, this work will provide precise measurements relevant to the advances in H2+ theory, which are necessary in other areas such as ultracold molecules and interstellar chemistry. The new measurements will also provide immediate improvement to the best existing spectral measurement in H2+.
The Resonant Excitation Stark Ionization Spectroscopy (RESIS) method has proven an excellent tool in the study of these high-L Rydberg states of several atoms, molecules and ions. The RESIS apparatus consists of an ion beam which is collided with a gas target in which the ions capture electrons. The now neutral beam will pass through an initial stripping field to remove any background states of n>15. Then a Doppler-tuned CO2 laser excites a transition between principle quantum states, for instance n=9 to 20. An electric field Stark ionizes the upper state of the transition and the resulting ions (signal) can be collected.
Students conducting research on this project will gain experience including both the application of classroom knowledge to experiment and tangible laboratory skills. In a broader sense, the students will be able to observe and experience first-hand what scientific research is like at an early stage in their career. More specifically they can expand their skills and basic understanding in different areas of scientific equipment use and design. They can develop a working knowledge of vacuum technology and equipment with the beamline apparatus. Students have spent time working with various electronics, including both design and repair of circuits. LabView experience can be gained through the use of the current equipment automation programs and the data acquisition system. The student training also provides for the development of their professional skills as a final outcome. All of my research students are required at a minimum to present a poster at an on campus research symposium. The annual Student Research and Creativity Exposition is sponsored by the Office of Student Creative Activity and Research (OSCAR) whose mission is to promote and support student scholarly activity and creative work across the SUNY Fredonia campus. Such student endeavor is integral to the teaching and learning experience and provides an opportunity for students to become closely affiliated with a faculty mentor and to develop skills and knowledge that will benefit them in the future.
Teaching Interests and Specialties:
- Lab and Lecture Demonstration Based Instruction
- Classroom group work with some peer instruction
- One on One additional instruction outside the classroom
- E. L. Snow and S. R. Lundeen, "Fine Structure Measurements in high-L n=17 and 20 Rydberg states of barium", Phys. Rev. A, 76, 052505 (2007).
- E. L. Snow and S. R. Lundeen, "Higher-order contributions to fine structure in high-L Rydberg states of Si2+", Phys. Rev. A, 75, 062512 (2006).
- L. E. Wright, E. L. Snow, S. R. Lundeen, and W. G. Sturrus, "Optical spectroscopy of high-L Rydberg states of argon", Phys. Rev. A, 75, 022503 (2007).
- E. L. Snow, M. A. Gearba, R. A. Komara, S. R. Lundeen, and W. G. Sturrus, "Determination of dipole and quadrupole polarizabilities of Ba^+ by measurement of the fine structure of high-L n=9 and 10 Rydberg states of barium", Phys. Rev. A, 71, 022510 (2005).
- E. L. Snow, R. A. Komara, M. A. Gearba, and S. R. Lundeen, "Indirect spin-orbit interaction in high-L Rydberg states with ^2S_1/2 cores", Phys. Rev. A, 68, 022510 (2003).
Contact me at:
NEW phone:(716)-673-4625, fax (716)-673-3347, or e-mail at email@example.com