Misassignment of the Multiplicity Forbidden Transitions in Pyridine

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Abstract
Experimental work is described which indicates that the two previously assigned singlet-triplet transitions for pyridine, in the regions 29 000—33 000 cm—1 and 25 000 — 28 500 cm—1 are due to impurities. The higher energy absorption is shown to be due to an impurity of pyrazine in pyridine to the extent of 1 part in 150 000. This pyrazine impurity is shown to be responsible also for causing the apparent phosphorescence emission of pyridine in the region 26 600 to 20 000 cm—1.