High-resolution measurements of the (ν1+ ν2)Qbranch of pure CO2were made using a difference frequency spectrometer with resolution of 5 × 10−5cm−1and a signal-to-noise ratio of 2000:1. LinesQ(2) throughQ(32) were measured with up to 14 lines in a single spectrum. The analysis of the branch has been performed on data taken at 301 K and pressures less than 11 kPa. The spectra were analyzed on a line-by-line basis within the Rosenkranz approximation of weak overlap [P. W. Rosenkranz,IEEE Trans. Antennas PropagationAP-23,498 (1975)]. The lineshape profile included Doppler broadening and Dicke narrowing [R. H. Dicke,Phys. Rev.89,472 (1953)] using a modified hard collision model [S. G. Rautian and I. I. Sobel'man,Sov. Phys. Uspekh.9,701 (1967)] with line mixing. For each line the broadening, Dicke narrowing, and line-mixing coefficients were determined. The broadening coefficients are in good agreement with measurements of lines belonging to different CO2bands. Our measured line-mixing parameters are compared to those predicted by a relaxation matrix which was calculated from an exponential power gap (EPG) law [L. L. Strow, D.C. Tobin, and S.E. Hannon,J. Quant. Spectrosc. Radiat. Transfer52,281 (1994)]. The vibrational band intensity and the linear pressure shift of the branch were also measured.