A collaborative experimental and theoretical study of rotationally inelastic collisions of CN(A (2)Pi,upsilon = 3,N = 60) fine-structure Lambda-doublet levels with argon is presented. Experimental state-to-state rate constants were determined with an optical-optical double resonance technique. The CN radical was prepared by 193 nm photolysis of BrCN diluted in slowly flowing argon at a total pressure of similar to 0.9 Torr. Specific levels of CN(A (2)Pi,upsilon = 3,N = 60) were prepared by excitation with a pulsed dye laser on various rotational lines in the A (2)Pi-X (2)Sigma(+)(3,0) band, and collisionally populated levels were probed after a short delay by laser fluorescence excitation in the B (2)Sigma(+)-A (2)Pi(3,3) band. Final state distributions (relative state-to-state rate constants) are reported. To calibrate their magnitude, absolute total removal rate constants and the large state-to-state rate constants for Delta N = -1 fine-structure conserving, Lambda-doublet symmetry-conserving transitions were determined. The measured rate constants were compared with theoretical rate constants computed in a quantum scattering treatment of the dynamics with ab initio CN(A (2)Pi)-Ar potential energy surfaces. The agreement of measured and computed rate constants is very good. The rate constants display dramatic Lambda-doublet propensities which depend upon the reflection symmetry of the initial level. From examination of coupled-state partial cross sections as a function of the projection quantum number specifying the angle of approach of the Ar atom to the CN plane of rotation, these propensities are shown to arise from a "helicopter" approach orientation which facilitates curve crossings between effective potential energy curves correlating with different rotational asymptotes. (C) 2000 American Institute of Physics. [S0021-9606(00)01610-X].