MOLECULAR BEAM STUDY of $AIND_{3}$ COMPLEX: STRUCTURE, VIBRATIONAL FREQUENCIES, and IONIZATION POTENTIAL.
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Date
1999
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Ohio State University
Abstract
$AIND_{3}$ complexes are produced in a Smalley-type laser ablation source and probed by resonance 2-photon ionization technique. In the range $18500-23500 cm^{-1}$, several vibronic bands for five isotopomers, $Al^{14}NH_{3}, Al^{15}NH_{3}, Al^{14}ND_{3}, Al^{14}NHD_{2}$, and $Al^{14}NH_{2}D$, are observed. Only the $AlND_{3}$ complex is studied in detail. The spectrum is assigned to the $\tilde{B}^{2}A-\tilde{X}^{2}E$ electronic transition, with the $\tilde{B}^{2}A_{1}$ and $\tilde{X}^{2}E$ states correlating to the $Al(4s)+ND_{3}({^{1}}A^{\prime}_{1})$ and $Al(3p)+ND_{3}({^{1}}A^{\prime}_{1})$ asymptotes, respectively. The $AIND_{3}$ complex has approximate $C_{3o}$ symmetry in both states. The origin band of the $\tilde{B}^{2}A_{1}- \tilde{X}^{2}E$ transition is located at $18532.5 \pm 1.0 cm^{-1}$. The spin-orbit splitting of the ground state is determined to be $55.7 \pm 0.4 cm^{-1}$. Frequencies of the $\nu_{3} (Al-ND_{3}$ stretch), $\nu_{4} (AlN-D_{3}$ symmetric stretch), and $\nu_{6} (Al-ND_{3}$ bend) vibrations in the $\tilde{B}^{2}A_{1}$ state are measured to be $315.7 \pm 0.6 cm^{-1}, 2657 \pm 1 cm^{-1}$, and $411 \pm 1 cm^{-1}$, respectively. Partially resolved rotational structure of some of the bands is observed and analyzed. The adiabatic ionization potential of the $AIND_{3}$ complex is measured by photoionization efficiency technique as equal $39710 \pm 10 cm^{-1}$. Rydberg series converging to various levels of the $Al^{+}-ND_{3}$ stretching mode of the $AlND_{3}^{+}$ cation are observed. The $\nu^{+}_{3}$ frequency is determined to be $322 cm^{-1}$. The structure determination of the neutral and monopositive complex and assignment of vibrational modes are aided by ab initio calculation.
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Author Institution: Steacie Institute for Molecular Sciences, National Research Council of Canada