ABSTRACT
The fact that aliphatic hydrocarbons had an absorption band at 1.7 µm was known as early as 1881.1 The assignment of this absorption as a Œrst overtone of a C-H stretch vibration was perhaps Œrst recognized by Joseph Ellis, although he initially felt that the 1.7 µm peak was part of a harmonic series that began with the 6.9 µm CH bending mode.2 Nevertheless, the assignment of the Œrst overtone of carbon-hydrogen stretching vibrations was made very early in the history of near-infrared spectroscopy.
