High resolution jet-cooled infrared absorption spectra of (HCOOH)(2), (HCOOD)(2), and HCOOH-HCOOD complexes in 7.2 mu m region

摘要

The rotationally resolved infrared spectra of (HCOOH)(2), (HCOOD)(2), and HCOOH-HCOOD complexes have been measured in 7.2 mu m 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 v(21) (H-C/O-H in-plane bending) fundamental band of (HCOOH)(2), the v(15) (H-C/O-D in-plane bending) fundamental band of HCOOH-HCOOD, and the v(20) (H-C-O in-plane bending) fundamental band of (HCOOD)(2). Strong local perturbations caused by the rotation-tunneling coupling between two tunneling components are observed in (HCOOH)(2). The v(21) fundamental band of (HCOOH)(2) and the previously measured v(22) fundamental and v(12) + v(14) combination bands [K. G. Goroya et al., J. Chem. Phys. 140, 164311 (2014)] are analyzed together, yielding a more precise tunneling splitting in the ground state, 0.011 367(92) cm(-1). The bandorigin of the v(21) band of (HCOOH)(2) is 1371.776 74(8) cm(-1), and the tunneling splitting decreases to 0.000 38(18) cm(-1) upon the vibrational excitation. The vibrational energy is 1386.755 49(16) cm(-1) for the v(15) vibrational mode of HCOOH-HCOOD and 1391.084 39(17) cm(-1) for the v(20) vibrational mode of (HCOOD)(2). No apparent spectral splittings are resolved for HCOOH-HCOOD and (HCOOD)(2) under our experimental conditions. The tunneling splitting in the ground state of HCOOH-HCOOD is estimated to be 0.001 13 cm(-1) from its average linewidth. Published by AIP Publishing.