Infrared absorption spectra of hydrogen complexes in type I diamonds

Abstract

The 3107 cm −1 peak has been observed in the infrared absorption spectra of all but one of some 50 type I diamonds examined. Evidence is presented which strongly supports the interpretation of this peak as being due to a carbon-hydrogen bond stretching mode. Reasons are given for believing that the hydrogen responsible for this, and the associated 1405 cm −1 line, is present as a constituent of the vinylidene group( > C = CH 2). Several new peaks, of fairly general occurrence, are reported in the wavenumber range 3400 cm −1 to 2750 cm −1. Some of these lines, seen only when the specimens exhibit at least partial type Ib character, are almost certainly due to nitrogen-hydrogen bond stretching. Others, found in type Ia and/or partially type Ib specimens may be due to C-H or N-H stretching in different local environments. Our observations show that hydrogen is as ubiquitous an impurity in diamond as nitrogen. Possible sites within the crystals for these hydrogenous groups are discussed.