The Fundamental Terahertz Mode of L-Alanine: Strong Narrowing, More Symmetry and Small and Non-Uniform Shift as Temperature is Reduced

We have measured the spectrum of L-alanine in the terahertz region over a wide temperature range. At the lowest temperature, the fundamental line at 2.21 THz is very sharp, 0.02 THz (0.8 cm
^-1
). As temperature increases, the line broadens, undergoes a non-uniform red shift, becomes more asymmetrical and decreases in oscillator strength.