The emission spectroscopy of AlD in the visible region: experimental and theoretical investigations

- VIS Fourier transform emission spectroscopy was applied.
- High-resolution spectra of the A?X and C?A systems of AlD were recorded.
- Global fit of the pure rotational, ro-vibrational and electronic spectroscopic data of AlD was made.
- Improved molecular constants of the X-, A- and C-states of AlD were obtained.
- New ab initio potentials for the X-, A- and C- states including spin-orbit coupling calculated.

The emission spectrum of the AlD isotopologue has been experimentally studied using Fourier transform spectroscopy in the 17,700−28,500 cm−1 spectral region. AlD molecules were produced within an aluminum hollow-cathode lamp with two anodes in the presence of 2.7 Torr of Ne and 0.2 Torr of ND3. The observed bands have been assigned to the A 1Π− X 1Σ+ (0−0,1 and 1−0,1,2,3 bands) and C 1Σ+− A 1Π (0−0 and 1−1 bands) transitions. In total, more than 450 rotational frequencies were measured with an absolute accuracy of about 0.002 cm−1. The current data have been combined with available measurements of the pure rotational lines by Halfen and Ziurys [Astrophys J 2010; 713: 520-523] and with the ro-vibrational bands by White et al. [J Chem Phys 1993;99:8371-8378] to provide improved spectroscopic constants of the X 1Σ+, A 1Π and C 1Σ+ states of AlD. These results match closely theoretical values obtained using a new set of ab initio potentials calculated with a spin-orbit Hamiltonian.

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