An ab Initio Study of the Ã2Π State and the Ã2Π←X̃2Σ+ Electronic Transition of MgNC

A Theoretical Study of MgNC and MgCN in the X̃2Σ+ Electronic State

“…The exponents and contraction coefficients are 15.006 (0.086911), 4.2875 (0.593580), and 1.225 (0.489612), where the contraction coefficients are given in parentheses. This basis set will be denoted as TZ3P + f. 5 The suitability of these basis sets, in terms of giving potential energy surfaces sufficiently accurate to predict spectroscopic constants that compare well with experimental values, has been demonstrated in our previous papers for theX 2 + states of MgNC and MgCN (3,4) as well as for theà 2 state of MgNC (8)(9)(10). Table 1 summarizes the equilibrium geometries, rotational constants, and transition state geometries for MgNC and MgCN calculated in the present work and compares them with experimental data (2,20) and with values obtained in previous calculations (3,4,6,7,12,18,(30)(31)(32).…”

“…to the equilibrium energy ofà 2 MgNC) are 809 cm −1 and 1940 cm −1 , respectively (8,9). In the present work, we have calculated potential energy values for MgNC and MgCN using the ACPF (Averaged CoupledPair Functional) ab initio MO method (11) with the basis sets TZ3P + f for Mg and TZ2P + f for N and C (see below for a more accurate characterization of the basis set).…”

“…If the molecular states are degenerate, that is, if there is more than one eigenfunction int (or int ) corresponding to the eigenvalue E (or E ), we calculate the linestrength by adding the individual transition probabilities for all transitions between the degenerate states; this is indicated by the sum over int and int in Eq. [9]. In this equation, µ A is the component of the molecular dipole moment operator along the A axis (A = X , Y or Z ); the (X, Y, Z ) axis system having origin at the molecular center of mass and space fixed orientation (see Chapter 14 of Ref.…”

“…1). The first excited electronic stateà 2 is doubly degenerate at linearity and thus subject to the Renner effect and to spin-orbit interaction (8)(9)(10). Also in this state, the barrier to MgNC/MgCN isomerization is low.…”

“…Also in this state, the barrier to MgNC/MgCN isomerization is low. At the MR-SDCI/cc-pVTZ level of calculation, the equilibrium energy of A 2 MgNC is 2405 cm −1 higher than that ofà 2 MgCN (8,9). In the lower (1 2 A ) and upper (2 2 A ) Renner-degenerate electronic states, the barriers to isomerization (measured relative…”