Judicious selection of polarization characteristics in degenerate four-wave mixing (DFWM) spectroscopy is shown to provide a facile and robust means for discriminating rovibronic features according to their changes in rotational angular momentum, DeltaJ. Building upon a perturbative (weak-field) treatment of the resonant DFWM response, theoretical analyses are presented for a collinear arrangement of linearly polarized electromagnetic waves that interact with an isotropic ensemble of gas-phase target molecules. The polarization unit vectors for two input fields (E-1 and E-3) are presumed to be fixed along the Y-axis (phi(1)=phi(3)=pi/2), while the remaining incident field (E-2) has its orientation within the transverse X-Y plane specified by angular coordinate phi(2). For phi(2)=pi/4, complete elimination of high-J Q-branch (DeltaJ=0) and P-/R-branch (DeltaJ=+/-1) structure is found to occur when the detected direction of linear polarization is switched between the limiting values of phi(4,Q)=-18.43degrees and phi(4,P/R)=+26.57degrees, respectively. These predictions are corroborated experimentally by probing the tunneling-split origin region of the tropolone A B-1(2)-X (1)A(1) (pi(*)<--pi) absorption system under ambient, bulk-gas conditions. Other polarization-based schemes for rovibronic branch suppression are discussed as are the effects incurred by (strong-field) optical saturation phenomena. The implementations of DFWM suggested by this work should prove useful for dissecting and unraveling the congested spectra often exhibited by massive polyatomic species. (C) 2003 American Institute of Physics.