Detection of the tunneling-rotation transitions of malonaldehyde in the submillimeter-wave region and proton tunneling dynamics

Abstract

The tunneling-rotation transitions of malonaldehyde, consisting of more than 200 a-type Q-branch lines along with 50 R- and P-branch lines, were observed in the submillimeter-wave region of 590–760 GHz. The proton tunneling splitting in the ground state, ΔE0 = 647 046.1640(40) MHz [21.583 208 818(133) cm−1], and the tunneling-rotation interaction constant, F0 = 45.8004(24) MHz, were determined. In addition, the rotational and centrifugal distortion constants were determined for both the 0+ and 0− tunneling sublevels. The proton tunneling dynamics of malonaldehyde were studied using a linear trajectory model to explain the observed molecular constants, and the potential barrier height hb was determined to be 2196 cm−1.