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

A dense grid of reference lines in the hyperfine structure of the B-X transitions of molecular iodine ((127)I(2)) 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 (1varsigma 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 (1varsigma) 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. Copyright 2000 Academic Press.