Absorption bands of HCN in the photographic infra-red

Abstract

The infra-red absorption spectrum of HCN has previously been investigated photographically by Badger and Binder. Since their publication, plates have been available which are sensitive much further into the infra-red. The most recent Agfa plates have their maximum of sensitivity at 10600 A and have been used by us as far as 12300 A with a tungsten lamp or even 12900 A with the sun. We have now used these plates to investigate the infra-red absorption spectrum of HCN up to 12300 A. While Badger and Binder found only two very weak bands at 7912 and 8563 A we have found two rather strong bands at 10385 A and 11645 A which could be accurately measured and analysed. In adition we have found an interesting pressure effect on the line width. The whole infra-red spectrum of this molecule and the vibrational energy scheme has recently been discussed by Adel and Barker who have also measured several new bands in the far infra-red.