The coefficients eJ' j ::; 9, defining the potential-energy V(z) and coefficients of two other radial functions related to adiabatic and nonadiabatic effects have been determined for AIH in the electronic ground state X 1~... by a direct fit to the published frequencies and wavenumbers of vibration-rotational transitions of 27AI1H and 27AFH. The functions are valid in the range of internuclear distance/Ifr" m [1.24, 2.601. Some trends in the spectral properties of the group 13 hydrides AIH, GaH, InH and TIH are discussed. The possibility of determining the rotational rnagnetogyric factor~from the available data of only wavenumbers of vibration-rotational transitions is considered; an approximate value & --2.25 is deduced for 27AIIH.
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