Absolute frequency measurement of molecular iodine hyperfine transitions at 647 nm

TL;DR

This paper presents precise absolute frequency measurements of specific molecular iodine hyperfine transitions at 647 nm using a fiber-based frequency comb, achieving high stability and accuracy for potential use as a reference laser.

Contribution

The study provides the first high-precision measurements of iodine hyperfine lines at 647 nm with a fiber comb, including pressure shift data and stability analysis.

Findings

Achieved a frequency stability of 5×10^{-12} at 200 s

Determined pressure shift to be -8.3(7) kHz/Pa

Measured line centers with 21 kHz precision

Abstract

We report absolute frequency measurements of the molecular iodine P(46) 5-4 $a_{1}$, $a_{10}$, and $a_{15}$ hyperfine transitions at 647 nm with a fiber-based frequency comb. The light source is based on a Littrow-type external-cavity diode laser. A frequency stability of 5 $\times$ 10$^{-12}$ at a 200 s integration time is achieved when the light source is stabilized to the P(46) 5-4 $a_{15}$ line. The pressure shift is determined to be -8.3(7) kHz/Pa. Our determination of the line centers reached a precision of 21 kHz. The light source can serve as a reference laser for lithium atom spectroscopy ($2P \to 3P$).