On the effective temperature of large sunspot umbra using AlH molecular lines

In this work, the radiative transition parameters including Franck-Condon (FC) factors, r-centroids, electronic transition moment, Einstein coefficients, band strength, oscillator strength, lifetime and effective vibrational temperature have been computed for A(1)Pi - X-1 Sigma(+) and C-1 Sigma(+) - A(1)Pi systems of aluminium monohydride (AlH) molecule by the numerical integration method for the experimentally known vibrational levels using Rydberg - Klein - Rees (RKR) potential. The computed radiative transition parameters are tabulated. A significant number of well resolved AlH molecular rotational lines of A(1)Pi - X-1 Sigma(+) (0,0), (1,1) and (0,1) bands are identified in the sunspot umbral spectrum and the estimated effective rotational temperature has been determined as 2315 K, 2155 K and 1838 K respectively. The effective vibrational temperatures of the A(1)Pi - X-1 Sigma(+) and C-1 Sigma(+) - A(1)Pi systems are found to be 5682 K and 3472 K respectively. Hence, the radiative transition parameters and the effective temperatures confirm the presence of AlH molecule in sunspot spectra.

Automated summary

In this study, the radiative transition parameters of the aluminium monohydride (AlH) molecule were calculated using numerical integration method, and the presence of AlH in the sunspot spectra was confirmed by the identified rotational lines and effective temperatures. The computed parameters and temperature results support the existence of AlH molecule.