[en] In the scattering process of energetic ions, the contribution of the nuclear elastic scattering (NES) appears in addition to Coulomb scattering. The NES forms a knock-on tail (non-Maxwellian tail) in ion velocity distribution functions. When the knock-on tail is formed, energy spectra of particles produced by a nuclear reaction are distorted from Gaussian distribution. The vacuum ultra violet (VUV) and visible light (VIS) emission spectra of ⁷Li produced by the ⁶Li+d reaction are broadened by the Doppler effect. Characteristics of these broadened spectra depend on the shape of ion distribution functions. Therefore, the knock-on tails on the deuteron velocity distribution function could be observed by using the Doppler effect for the VUV and VIS spectra. Because high wavelength resolution instruments (∼ 10 pm in VUV, ∼ 4 pm in VIS) are available, detailed measurements of the size and shape of the knock-on tail by VUV and VIS spectroscopy might be possible. We evaluated the VUV and VIS spectra for the cases when a knock-on tail is formed and not formed assuming the hydrogen beam injected deuterium plasma. Clear difference of the Doppler broadening between the cases was seen. It is shown that the VUV and VIS emission spectra can be a useful tool for the knock-on tail observation. (author)