Measurements of Fine-Structure Intervals in High Angular Momentum Helium Rydberg States
A fast-atomic-beam technique using rf resonance and Doppler-tuned laser detection has been employed to measure the G-H, H-I, and I-K fine-structure intervals in n = 10 in helium. Helium atoms in high-angular-momentum states, which have been produced by passing a 11.5 keV He('+) beam through a gas target, are sent through a transmission line where rf transitions between adjacent L-states are driven. Detection of the rf transitions is accomplished by driving the n = 10 to n = 27 transition with a CO(,2) laser Doppler tuned to pump only a single L-state in n = 10. The highly excited atom (n = 27) is then Stark ionized and the remaining ion is detected. The electrostatic intervals for the n = 10, G-H, H-I, and I-K intervals are measured to be 490.986(.011) MHz, 157.064(.012) MHz and 60.814(.009) MHz respectively. Although the results for the H-I and I-K intervals are sufficiently precise to resolve the contribution to the structure of long-range "vacuum fluctuation" effects of the type described recently, they are inconsistent with the simplest estimates of these effects. However, the results also indicate that calculations of these intervals which neglect quantum electrodynamic effects are incomplete at the level of precision of this experiment.
- Pub Date:
- VACUUM FLUCTUATIONS;
- CASIMIR EFFECT;
- Physics: Atomic