Abstract

In a large part of the optical spectrum, extending from the green to the near infrared (500-900 nm) the Iodine Atlas [1] has become a useful tool for absolute frequency calibration. The accuracy of the Doppler-broadened lines, measured by Fourier-transform spectroscopic methods is however limited to 0.001 cm⁻¹ or 30 MHz at 1σ. In many applications there is a need for a more accurate standard. Indeed, in the past decades, several resonances of the I₂-spectrum have been measured to much higher precision, using primary wavelength standards and various forms of saturation spectroscopy unravelling the hyperfine structure of the rovibronic transitions. But these reference lines are spread erratically over the visible range.

© 2000 IEEE