[Study of collisional broadening of spectral line by optical-optical double resonance].

The collisional broadening of the 2(1)sigma+ --> 6(1)sigma+ line of NaK molecule was studied using the optical-optical double resonance technique. A single-mode diode laser was set to a particular 1(1)sigma+ (v", J") --> 2(1)sigma+ (v',J') transition. Another single-mode diode laser was then used to excite the molecule from 2(1)sigma+ (v', J') level to the rovibrational level of 6(1)sigma+. The two laser beams counterpropagated through the cell. The broadening rate coefficient was determined from the slope of the total linewidth versus potassium density curve. The rate coefficient, k(br) = (1.4+/-0.7) x 10(-8) cm3 x s(-1), was obtained. The collisional excitation transfer between rotational levels of the 2(1)sigma+ state [i. e., 2(1)sigma+ (v = 8, J = 12) --> 2(1)sigma+ (v = 8, J = 13, 14)] was also investigated. The rates can be determined from the relative intensities of the main peak and satellite lines, combined with a rate equation model. The rates are 6.1 x 10(6) and 5.2 x 10(6) s(-1) respectively.