Rotational Spectra of the Carbon Chain Negative Ions C ₄ H ^- and C ₈ H ^-

Abstract

The rotational spectra of the butadiyne anion C4H- and the octatetrayne anion C8H- have been detected in the laboratory. Precise spectroscopic constants for these closed-shell molecules have been obtained, which enable their rotational spectra to be calculated to high accuracy throughout the radio band. Deep astronomical searches can now be undertaken in essentially any molecular source, including TMC-1 and IRC +10216, where the negative ion C6H- has recently been detected. The large dipole moments and high binding energies of both anions make them good candidates for astronomical detection.