AbstractThis paper deals with the so-called ‘phonon maser’ due to the level splitting of deuterium imbedded in Al in a strong magnetic field. Since the wavelength of the phonon ranges around 0.1 mm, corresponding frequency of the phonon is in the radio frequency range. The present paper aims at an explanation of the anomalous melting of the Al surface implanted with deuterium on the irradiation with high energy electron in a transmission electron microscope. After theoretical and/or experimental examinations of several conventional mechanisms, all of them are classical processes and usually conceived by solid state or material scientists, we judged that the phenomenon cannot be accounted for by these classical processes, but require quantum theoretical mechanisms as a requisite. However, the present theory is rather preliminary and qualitative.