High Precision Measurements on Helium at 1083 nm
Authors: Cancio P., De Natale P., Giusfredi G., Pavone FS., Inguscio M.
Autors Affiliation: European Laboratory for Non-Linear Spectroscopy (LENS), Largo E. Fermi 2, I-50125, Firenze, Italy;
Istituto Nazionale di Ottica Applicata (INOA), Lg. E. Fermi 6, I-50125, Firenze, Italy;
Dipartimento di Fisica, Università di Perugia, Via Pascoli Perugia, Italy;
Dipartimento di Fisica, Università di Firenze, Largo E. Fermi 2, I-50125, Firenze, Italy
Abstract: We present a review of the helium spectroscopy, related to transitions between 23S and 23P states around 1083 nm. A detailed description of our measurements, that have produced the most accurate value of the 23P0 −23P1 fine structure interval, is given. It could produce an accurate determination (34 ppb) of the fine structure constant α. Improvements in the experimental set up are presented. In particular, a new frequency reference of the laser system has been developed by frequency lock of a 1083 nm diode laser to iodine hyperfine transitions around its double of frequency. The laser frequency stability, at 1 s timescale, has been improved of, at least, two orders of magnitude, and even better for longer time scales. Simultaneous 3He −4 He spectroscopy, as well as absolute frequency measurements of 1083 nm helium transitions can be allowed by using the I2-locked laser as frequency standard. We discuss the implication of these measurements for a new determination of the isotope and 23S Lamb shifts.
More Information: ISBN: 3540419357KeyWords: Quantum Physics; Atoms; Molecules; Clusters and Plasmas;