Spectroscopy of Hydrogenic Atoms Dennis V. Perepelitsa with Brian - - PowerPoint PPT Presentation

Spectroscopy of Hydrogenic Atoms

Dennis V. Perepelitsa with Brian J. Pepper

MIT Department of Physics October 23rd, 2006

Introduction

Theory

Bohr Equation – Balmer Series Rydberg Constant Mass Corrected Bohr Equation Hydrogen Isotope Shift

Experimental Setup

(Figure modified from “Optical Spectroscopy of Hydrogenic Atoms” Lab Guide.)

Equipment Jobin Yvon 1250 M Monochromator Species Mercury (Hg), Sodium (Na), Hydrogen & Deuterium (H) Precision 1800 gvs./mm. - σ (repeatability) = .02A 3600 gvs./mm. - σ (repeatability) = .01A (but 3600 gvs./mm. scans only < 5000 A) Procedure * Wide scans at 1A * Calibration from Mercury using beam splitter * Lines focused and centered on entrance slit * Scans conducted with both gratings

Calibration and Fitting

Voigt Profile Mercury Calibration Offset

(http://wikipedia.com.)

Hg: 3650 A, 4047A, 4358A, 5460A, 5770A

Data

(Hydrogen Balmer 4 -> 2 line, 3600 gvs./mm.)

Hydrogen Balmer Series

Calculation of the Rydberg Constant

Hydrogen Isotope Shift

Conclusions

Hydrogen Balmer Series Rydberg Constant Hydrogen Isotope Shift

(How good are the results?)

1800 gvs./mm. data agrees with accepted values to within the error. 3600 gvs./mm. is less accurate, but more precise. ➔ Balmer series measured to nearest ~.08 A of accepted values.

• vs. (Accepted)

➔ Measured to within 1% of accepted value. vs. (Accepted) ➔ Measured to within .01% of accepted value. ➔ But! - Error bars too small! Too many sig figs! Systematic error? Bad methodology? Imprecise equation?

Acknowledgments

Brian Pepper, an equal partner in collecting and analyzing the experimental data. Professor Isaac Chuang, who answered our questions about the experiment and pointed us in the right direction.

• Dr. Scott Sewell, and Scott Sanders,

who helped us in our research and talked about spectral line width with us.