TOWARD THE ASTRONOMICAL DETECTION OF THE PROTON-BOUND COMPLEX NN–HCO+: IMPLICATIONS FOR THE SPECTRA OF PROTOPLANETARY DISKS

Abstract

ABSTRACT Proton-bound complexes have been hypothesized as further means of detecting the nitrogen molecule in the interstellar medium. The study of such complexes has largely been hindered by the necessary experimental setups utilized or by their difficulty in producing and/or analyzing computed potential energy surfaces. Here the NN–HCO+ proton-bound complex is analyzed via quartic force fields (QFFs). While QFFs have produced meaningful results for other proton-bound complexes, they have been hindered by double-well potentials or flat potential surfaces. NN–HCO+ is not affected by these constraints. This strongly dipolar (3.63 D) molecule can be observed rotationally unlike the more heavily analyzed OCHCO+ and NNHNN+ proton-bound complexes. Additionally, the large absorption feature corresponding to the proton motion, a hallmark of proton-bound complexes, is much higher in frequency at 2547.1 cm−1, changing the range of experimental observation for the bright frequency. NN–HCO+ is hypothesized to be present in protoplanetary disks where N2H+ and CO are known. As such, it may help to influence the nitrogen budget of planet-forming astronomical regions.