Singlet and triplet states of the CO3 and CO4 molecules

Carbon Tetraoxide: Theoretically Predicted and Experimentally Detected

“…Thus, one is left with singlets 5 and 6, whose dissociation into CO 2 (X 1 AE + ) and O 2 (a 1 D) is also exothermic, and hence their detectability depends on the existence of sizable kinetic barriers to dissociation. This rules out 5, as no such a barrier could be identified, thus restricting the choice to singlet 6, whose dissociation into CO 2 (X 1 AE g + ) and O 2 (a 1 D g ) is forbidden by orbital symmetry rules [5,7] and hence can be expected to have a significant barrier, [32] in addition to that presumably arising from steric factors. [7] However, an indirect route to dissociation could involve fast nonradiative singlet-triplet decay of 6 into 7, prone to dissociation into CO 2 …”

“…Fortunately, the barrier to the nonradiative decay of 6 into 7, and hence the barrier to dissociation of 6, has been investigated in details by Averyanov, Khait and Puzanov, [7] whose estimate sets the barrier height in the range from 15.0 to 27.3 kcal mol À1 . Among the ionic precursors of 6 in our NR experiments, only 3 has the same connectivity as 6, whereas its geometry is similar but not identical to that of the neutral molecule.…”

“…Another isomer of C 2v symmetry has been identified on the potential energy surface (PES) of the lowest 1 A 1 singlet state, and two local C 2v minima have been located on the low-lying, excited triplet PES. [7] In summary, the available theoretical results identify two singlets of D 2d and C 2v symmetry as the lowest energy CO 4 …”

“…[4] CO 4 is of special interest, since ab initio MP2, QCISD and MP2/6-31G* calculations [5][6][7] have identified a CO 4 D 2d 1 A 1 singlet as a metastable species that releases from 80 to 93 kcal mol À1 upon dissociation into CO 2 (X 1 AE + ) and O 2 (a 1 D). Another isomer of C 2v symmetry has been identified on the potential energy surface (PES) of the lowest 1 A 1 singlet state, and two local C 2v minima have been located on the low-lying, excited triplet PES.…”

Carbon Tetraoxide: Theoretically Predicted and Experimentally Detected

“…More importantly, members of the CO n family are potential high‐energy density materials (HEDM), the next generation of environmentally benign propellants and explosives 4. CO 4 is of special interest, since ab initio MP2, QCISD and MP2/6‐31G* calculations5–7 have identified a CO 4 D 2 d 1 A 1 singlet as a metastable species that releases from 80 to 93 kcal mol −1 upon dissociation into CO 2 (X 1 ∑ + ) and O 2 (a 1 Δ). Another isomer of C 2 v symmetry has been identified on the potential energy surface (PES) of the lowest 1 A 1 singlet state, and two local C 2 v minima have been located on the low‐lying, excited triplet PES 7.…”