Knowledge Bank

The discovery of the Impurity-Helium Solid Phase $(IHSP)1$ allows to achieve a reliable long-time isolation of metastable species by helium. The long-lived nitrogen $N(2D)$ atoms seem to be a persuading spectroscopic object here. They turn out to survive more than $104$ s in IHSP with radiative decay caused solely by a heavy particle (nitrogen molecule or rare gas atom) $neighborhood2$. The comparison of atomic $N(2D\to \mathrm{<mrow\; data-mjx-texclass="ORD">4</mrow>}S)$ at $\lambda \approx 520$ nm and atom-molecular vibronic $N(2D)-N2(/nu=0)\to N(4S)-N2(/nu=1)$ at $ \lambda \approx 595$ nm luminescences have confirmed that the molecular-like spectra shapes are consequense of the excimer state formation. The excimer-like nature of isolated $N(2D)$- Rg pairs $(Rg\equiv Ne,Ar,Kr,Xe)$ is evidenced by their both spectra shapes and luminescence lifetimes observed. Thermoluminescence studies give the energy barrier for two isolated in IHSP neighboring heavy particles fusion, $Eact=40\pm 4K2$. In contrast LIF study of the isolated in IHSP solitary $Ne(3P2)$ atoms has shown the lines nonbroadened and nonshifted with experimental accuracy of $0.06\backslash AA$, in spite $Ne(3P)$ atom is close analog of alkali ones for which large spectra disturbance by both liquid and solid helium have been elucidated.