The rotationally resolved infrared spectra of (HCOOH)2, (HCOOD)2, and HCOOH-HCOOD complexes have been measured in 7.2 μm region by using a segmented rapid-scan distributed-feedback quantum cascade laser absorption spectrometer to probe a slit supersonic jet expansion. The observed spectra are assigned to the v21(H-C/O-H in-plane bending) fundamental band of (HCOOH)2, the v15(H-C/O-D in-plane bending) fundamental band of HCOOH-HCOOD, and the v20(H-C-O in-plane bending) fundamental band of (HCOOD)2. Strong local perturbations caused by the rotation-tunneling coupling between two tunneling com...
