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

Abstract

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 A1Π−X1Σ+ and C1Σ+−A1Π 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 A1Π−X1Σ+ (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 A1Π−X1Σ+ and C1Σ+−A1Π 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.