Knowledge Bank

Electron spin resonance (ESR) signals attributed to the linear $C4,C6,C8$, and $C10$ molecules in their lowest 3E states, oresunably their ground states, have recently been observed in solid neon and argon matricies at $\mathrm{<mrow\; data-mjx-texclass="ORD">4</mrow>}K1$, Hyperfine interaction in the $\mathrm{<mrow\; data-mjx-texclass="ORD">13</mrow>}Cn$ molecules was small, indicating cumulene-line bonding with the unpaired spins in p orbitala. The zero field splitting parameters, (D), were found to be 0.236, 0.363, 0.783, and $0.190cm-1$, respectively, in solid neon. Ab initio molecular orbital calculations have been performed to help interpret this data. The increase in (D) through $C8$ is attributed to a corresponding variation in the spin-orbit coupling with low lying states, principally the 1Eg as the chains lengthen. Gross orbital spin populations and energy difference, were obtained from Hartree-Pock calculations is order to interpret the his and (D) data, respectively. Fot $C4$ and $C6$ electron correlation was included via second $(MP2)$ and third $(MP3)$ order Moller-Plesset perturbation theory.