CN rotational excitation

Abstract

Abstract We demonstrate, using a sample of high quality spectra, that the average equivalent width ratio of the unsaturated R(0) and R(1) lines of the CN B 2 Σ + – X 2 Σ + (0, 0) band near 3875 Å equals π instead of 3.73 – calculated for the CMBR temperature T = 2.725 K and the already published oscillator strengths of both transitions, i.e. the excitation temperature of CN is slightly higher than it should be expected if CMBR is the only excitation mechanism. Taking into account the saturation effects by means of profile fitting during the column density calculations does not remove the revealed temperature excess. Possible interpretations of the effect are discussed (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)