MM-Wave Field Effects Upon Optical Properties of Aminoacid Crystals

Investigation of the mm-wave (MMW) or extremely high frequency (EHF) radiation effect upon optical properties of α-glycine and β-alanine aminoacids was carried out by infrared (IR) reflection spectroscopy. MMW irradiation frequency was tuned in the range of 37-300 GHz. Incident power density of radiation varied from 10 to 100 W/m². Drastic changes in shape and band intensity in the 800-1600 cm^-1 range were detected under MMW radiation action. There emerged an optional fine structure, depending on IR and MMW radiation polarization. The deformational vibrations of NH⁺3 and COO^- groups in aminoacids were more sensitive to MMW radiation. A resonance character of MMW influence was determined. More than 20 resonances for alanine and 10 resonances for glycine were observed. Halfwidth of MMW radiation effect defined after NH deformational vibration changes was about 60-80 MHz. Amplitude of changes of the IR band intensities approached +.80% starting from initial intensity. As it was shown by the measurements, specimens temperature control (accurate to 0,5 K) did not vary in the process of changes. Nevertheless, the temperature control experiments demonstrated that specimens heating up to 320 K resulted in the well-known temperature widening of IR bands distinctly different from MMW radiation effect. The data obtained may be regarded as non-trivial and to explain them it would be appropriate to recruit the ideas of non-linear dynamic processes being, moreover, of collective nature. In particular, the possibility of multiphoton excitations in EHF field does not seem to be groundless because in permanent or low-frequency electromagnetic field lifetime of vibrational-rotational states may increase by several orders comparatively to visible range. Therefore, MMW irradiation may result in distribution not only in rotational states, but it may also change molecular redistribution in vibrational states. The multiformity of multiatomic molecule vibrational levels, the presence of numerous possibilities of Fermi-resonance manifestation, and in solid state - of Fermi-Davydov resonance - these factors add greatly to the probability of resonance interaction between EHF field and quasicontinuous spectrum of rotational-vibrational state of alanine and glycine.