On the Rotational Temperature of AlH in Sunspots

A search has been carried out for the presence of rotational lines of two bands of the (0, 0) and (1, 1) A 1Π – X 1Σ+ system of the AlH molecule in the high resolution Fourier Transform Spectra of sunspots observed at the National Solar Observatory at Kitt Peak. Though the presence of the AlH molecule in sunspots was confirmed by Wallace, Hinkle, and Livingston (An Atlas of Sunspot Umbral Spectra in the Visible from 15 000 to 25 000 cm−1 (3920 to 6664 Å), Tech. Rep. 00-001, National Solar Observatory, Tucson, AZ, 2000), there is no report on the rotational temperature in the literature by identifying AlH molecular lines. The results obtained in this new search using a suitable identification technique are compared with the results reported by Wallace, Hinkle, and Livingston (2000). In view of the fact that the rotational temperatures of the molecules could be used to test photospheric and sunspot models, the effective rotational temperature for the (0, 0) band of the A – X system of AlH molecule is estimated by measuring the equivalent widths of well resolved spectral lines and its value justifies the existence of the AlH molecule in sunspots.