Computational molecular spectroscopy for NiCN: Large-amplitude bending motion

Ab initio molecular orbital study of ground and low-lying electronic states of NiCN

“…The experimentally determined r 0 values could correspond to our projected averaged values since the experimental determination of r 0 is made under the assumption of a linear average structure so that the effects of the large-amplitude bending motion are neglected entirely. From the 3D PES [28] we compute an effective rotational constant of B 0 = 0.14512 cm À1 ; it differs by only 0.3% from the experimental B 0 value in Ref. [24] which, unlike the r 0 values, can be derived from the observed spectrum in a straightforward manner.…”

“…It should be noted that we are comparing here ab initio values for the equilibrium bond lengths r e with experimentally determined values for the vibrationally averaged bond lengths r 0 , and so the comparisons should be taken with some slight caution. We are currently [28] calculating theoretical r 0 values for e X 2 D NiCN, obtained as expectation values over MORBID [12][13][14][15] rotation-vibration wavefunctions computed from a three-dimensional PES determined at the same ab initio level of theory. We obtain hr(Ni-C)i 0 = 1.8159 Å and hr(C-N)i 0 = 1.1705 Å with the averaged projection of each bond length onto the molecular axis being 1.8130 and 1.1603 Å , respectively.…”

“…For the electronic ground state 2 D i , the comparison of the experimentally derived r 0 structure with the rovibrationally averaged structure determined from a full-dimensional ab initio PES has been briefly outlined to demonstrate the accuracy of the present calculations. A detailed discussion of the r 0 structures, based on the results of variational calculations carried out with the MORBID [12][13][14][15] program, will be reported elsewhere [28].…”

“…We further report comparisons of the properties for the low-spin and highspin states that we characterize, and we discuss the spinorbit interaction scheme for NiCN. A detailed discussion, in terms of rovibrationally averaged molecular parameters, of the effects of large-amplitude bending motion in NiCN will be reported elsewhere [28].…”

The predicted spectrum of FeOH in its Renner-degenerate and electronic states

“…We have already reported ab initio MO studies for several firstrow transition-metal-containing molecules such as FeNC [10], FeCN [11], CoCN [12,13], and NiCN [14,15] and have predicted the spectroscopic properties of the molecules, in particular the effects of the large-amplitude bending motion. For FeOH, our initial ab initio MO calculations, carried out at a highly correlated level of theory, were motivated by astrochemical interest.…”