Sentence:  One sample , which had been exposed to the atmosphere after evacuation at 375 ` C , showed the presence of adsorbed water ( about 0.3 wt % ) as evidenced by a weak <WSD>resonance</WSD> line which was very narrow at room temperature and which disappeared , due to broadening , at low temperature . 
Meaning of the word marked with <WSD> tags:  an excited state of a stable particle causing a sharp maximum in the probability of absorption of electromagnetic radiation