Heterodyne frequency measurements of 13CO2 laser hot band transitions

Careful measurements by means of stabilized CO2 lasers are presented for the frequencies of 28 lines in the P-branch of the 01 0 0-(11 1 0, 03 1 0)I band of (C-13)(0-16)2, observed in laser emission, and three lines in the R-branch, observed in absorption with a diode laser. A significant improvement in the ro-vibrational constants has been obtained from a least squares fit to these data, demonstrating that the laser lines stabilized by natural absorption techniques provide convenient, accurate frequency references near 11.7 microns with an uncertainty of less than 0.1 MHz.