Spectroscopic investigations on AlH(X1Σ+) radical using multireference configuration interaction theory in combination with correlation‐consistent quintuple basis set augmented with diffuse functions

Abstract

AbstractThe equilibrium internuclear separations, harmonic frequencies, and potential energy curves (PECs) of the AlH(X1Σ+) radical have been investigated using the highly accurate valence internally contracted multireference configuration interaction (MRCI) approach in combination with a series of correlation‐consistent basis sets in the valence range. The PECs are all fitted to the Murrell‐Sorbie function, which are used to reproduce the spectroscopic parameters (De, D0, ωeχe, αe, and Be). By comparison with the available experimental results, the PEC obtained at the basis set, aug‐cc‐pV5Z, is selected to investigate the vibrational manifolds. The present D0, De, Re, ωe, ωeχe, αe, and Be are of 3.0731 eV, 3.1775 eV, 0.16510 nm, 1683.37 cm−1, 29.3786 cm−1, 0.18876 cm−1, and 6.3663 cm−1, respectively, which almost perfectly conform to the available measurements. With the potential determined at the MRCI/aug‐cc‐pV5Z level of theory, the total of 26 vibrational states is predicted when the rotational quantum number J is set to equal zero (J = 0) by numerically solving the radial Schrödinger equation of nuclear motion with the Numerov method. The complete vibrational levels, classical turning points, inertial rotation, and centrifugal distortion constants are determined when J = 0 for the first time, which are in excellent agreement with the available experimental data. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2011