Optical free induction decay (FID) signals of the CH3F v(4) band were observed by using a cw-OPO infrared laser coupled with a Stark switching method. The observed signals have been Fourier transformed to obtain the Lorentz functions and the widths have been analyzed to determine the pressure-broadening coefficients for R-r(0,0), (r)Q(1,0), R-r(1,0), R-r(1,1), and P-p(2,1) to be 1/(pi T-2 p) = (46.1 +/- 2.1), (31.6 +/- 3.6), (21.8 +/- 2.5), (25.2 +/- 4.0), and (26.5 +/- 1.8) MHz/Torr, where T-2 is the transverse decay time. The value of rR(0,0) is larger than that determined from a recent pressure-broadening measurement by 39 +/- 12%. The difference is explained by collision induced reorienting transitions (Delta M = +/- 1, Delta J = 0). (C) 2017 Elsevier B.V. All rights reserved.