A Dense Grid of Reference Iodine Lines for Optical Frequency Calibration in the Range 595–655 nm

Abstract

A dense grid of reference lines in the hyperfine structure of the B–X transitions of molecular iodine (127I2) is presented. Frequencies of 481 “t”-hyperfine components in 15 vibrational bands covering the wavelength range 595–655 nm were determined with an absolute accuracy of 1.0 MHz (1ς uncertainty). Spectra were obtained by Doppler-free saturation spectroscopy using a cw ring-dye laser of 1-MHz bandwidth. Center-of-gravity frequencies of rovibronic lines, determined by correcting for the calculated hyperfine shift, are included separately in a least-squares parametrization for each band. From the obtained molecular constants a prediction is made for all t-hyperfine components of the 15 bands covering 595–655 nm. Hence a dense grid of reference lines of 1 MHz (1ς) absolute accuracy is created, with a line in each interval of 1 cm−1 in the entire range. This spectral atlas of about 3400 lines may provide a useful calibration tool in many laboratories.