Rotational spectroscopy of AlO

Abstract

Aims. The detection of rotational transitions of the AlO radical at millimeter wavelengths from an astronomical source has recently been reported. In view of this, rotational transitions in the ground X 2 Σ + state of AlO have been reinvestigated. Methods. Comparisons between Fourier transform and microwave data indicate a discrepancy regarding the derived value of γ D in the v = 0 level of the ground state. This discrepancy is discussed in the light of comparisons between experimental data and synthesized rotational spectra in the v = 0, 1 and 2 levels of X 2 Σ + . Results. A list of calculated rotational lines in v = 0, 1 and 2 of the ground state up to N = 11 is presented which should aid astronomers in analysis and interpretation of observed AlO data and also facilitate future searches for this radical.

Spectroscopy of AlO: Combined analysis of the A2Πi→X2Σ+ and B2Σ+→X2Σ+ transitions

“…However, we could confirm that the ground state c and c D parameters show a drastic dependence on the vibrational quantum number. We subsequently constrained B, c, c D and the hyperfine parameters of the v 00 6 2 levels to their microwave values [15,17,21], while systematically varying D for v 00 6 2 and B, D, c and c D for higher vibrational levels. At each step, we synthesized the entire B 2 R + ?…”

“…The hyperfine parameters, as well as B, c and c D of the v = 0-2 levels of the ground state have been taken from Refs. [15,17,21]. The hyperfine parameters of the v = 3-7 levels of the ground state have been set equal to the corresponding v = 2 values.…”

Rotational Spectra of Vibrationally Excited AlO and TiO in Oxygen-rich Stars

“…The millimeter-wave rotational spectra of AlO were directly measured in the laboratory in the v = 1 and v = 2 levels (Goto et al 1994) and are tabulated in Launila & Banerjee (2009) and CDMS 1 . The spectroscopic constants in the higher vibrational levels (v = 3, • • • , 7) of AlO were derived from rotationally resolved spectra of the two lowest electronic transitions (A 2 Π → X 2 Σ and B 2 Σ → X 2 Σ; Launila & Berg 2011).…”

“…to within a few MHz and are sufficient for establishing the identification of lines of vibrationally excited AlO in the astronomical spectra. The frequencies and relative intensities of the hyperfine components used to calculate the synthetic profiles of AlO in the v = 0, 1, and 2 levels are tabulated in (Launila & Banerjee 2009). The term energy for the v = 1 excited vibrational level is 1389 K and 2758 K for the v = 2 level.…”

“…The synthetic profiles of the lines in the v = 2 vibrational state were obtained by representing each hyperfine component with a Gaussian profile whose HWHM was 2.5 km s −1 . The relative intensities of the hyperfine components were equivalent to the theoretical relative intensities in Launila & Banerjee (2009). The variables in the least squares fit of the synthetic profile to the observed profile were: an intensity (scaling) factor of the composite theoretical synthetic profile and the center frequency.…”