The far‐infrared properties of polyamino acids

The far‐infrared absorption between 3 and 650 cm −1 of several amino acids and polyamino acids is measured under a variety of conditions. The far‐infrared spectra of amino acids and short‐chain oligomers are extremely temperature dependent with the appearance of numerous narrow absorption lines at 4.2 K. These absorption lines broaden or disappear at 300 K or for absorption measurements on samples in solution. For longer polymers, relatively broad nearly temperature‐independent absorption lines are observed with little difference between the spectra of polymers in solution or in the solid state. These results are explained in terms of the crystalline order of the samples.