Determination of the Rotational Constant A_0 and the Bending Angle CNC for CH_3 NC and CH_3 ^{15}NC Molecules


Abstract: The rotational constant A_0 for the ground state of CH_3 NC and CH_3 ^{15}NC isotopomers is calculated using a technique which was used earlier for CH_3CCH [9], CH_3CN [10] and SiH_3CCH [11]. This technique is based on calculating the moment of inertia tensors in the bent configuration due to the \nu_8 vibrational state, which is associated with the CNC bending vibration. These values of the moments of inertia are fitted with the values calculated from the rotational constant B_V, found experimentally by measuring the rotational frequencies in the microwave and infrared regions. From the fitting, the rotational constant A_0, the bending angle \angle CNC and the asymmetry parameter \kappa are determined for \nu_8 = 1, 2 and 3 bending vibrational states. The effect of the isotopic substitution of ^{13}C, ^{15}N and Deuterium on the angle \alpha is studied, which is found to be negligible.

Keywords: Methyl isocyanides; Rotational constants; Bending angle; Asymmetric parameter; Moment of inertia tensors.

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