Knowledge Bank

A method developed recently for studying spin.orbit (SO) Interactions (1) is here applied to calculating MCD spectra. The method can be briefly described as a first-order perturbation technique which involves solving the set of linear equations: $ (\bar{H^{o}}- E)\phi^{1}{1}- \tilde{H}^{p}\Phi^{o}{1}=(\tilde{H}^{P} some perturbing Hamiltonian)$ over Configuration State Functions (CSF's) to obtain the first-order correction $\gamma 1$; to the electronic state $\Phi i$. This partially alleviates the impossible task of attempting to calculate explicitly the infinite manifold of perturbing states represented in the usual expression for a first-order perturbation. [FIGURE] The MCD B term, which acquires it's intensity through such perturbations, can be calculated via eq. I thus avoiding the need to calculate explicitly the large number of excited states involved in the summation of eq. 2. Results are presented for this new application of the method to the singlet $X->B(1Bu)$ and $X->C(1Hu)$ transitions in acetylene.