Optical constants of solid ammonia in the infrared*

On the basis of transmission measurements of samples at temperatures near the melting point, we have determined the Lambert absorption coefficient α(ν) for solid ammonia in the spectral range 950–5300 cm−1. The imaginary part k of the complex index of refraction Nˆ=n+ik can be obtained from the defining relation k(ν) = λα(ν)/4π. Using the measured values of α(ν), we have employed subtractive Kramers–Kronig analysis to obtain the real part n(ν) of Nˆ in the range 960–5300 cm−1. In this analysis, we have used a computed value n(ν) at 4800 cm−1 based on a Lorentz–Lorenz relation and the value of n(ν) for liquid ammonia that we measured previously. The resulting optical constants k(ν) and n(ν) for solid ammonia are presented graphically and tabularly.