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Gray has criticized the calculation of the ground state multiplicity of the CH2 fragment by the author. In answer, I would like to make two comments.
1. Regardless of the energies of ionization of a carbon atom, CH2 may be considered as a system composed of two protons, a carbon kernel, and four electrons. The proper amount of configuration interaction should arise naturally and depend on relative energies of orbitals and overlap values. It appears that there is too much configuration interaction in the calculation in reference since the equilibrium angle arrived at is 160° instead of 140° as obtained by Herzberg. Nevertheless, the measured angle of 140° seems to the author to be considerably greater than a few degrees greater than 90° and to indicate a considerable amount of configuration interaction.
2. Noyes has obtained data on photocatalyzed gas reactions of hydrocarbons that give indications of the presence of CH2 fragments as intermediates. There is also a suggestion that these may be in triplet states. This certainly cannot be said to have been proved, however.