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Non-intrusive spectroscopic probing of weakly bound van der Waals complexes forming in gaseous carbon dioxide is generally performed at low pressures, for instance in supersonic jets, where the low temperature favors dimers, or in few-atmosphere samples, where the signature of dimers varying as the squared gas density is entangled with the dominating collision-induced absorption. We report experimental and theoretical results on CO2 dimers at very high pressures approaching the liquid phase. We observe that the shape of the CO2-dimer bands undergoes a distinctive line-mixing transformation, which reveals an unexpected stability of the dimers despite the collisions with the surrounding particles and negates the common belief that CO2 dimers are short-lived complexes. Our results furnish a deeper insight allowing a better modeling of CO2-rich atmospheres and provide also a new spectroscopic tool for studying the robustness of molecular clusters.

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The optical absorption, luminescence and EPR methods have been used to study LiH(D) single crystals doped with Ru2+. The formation of new absorption bands and EPR signal was observed after the illumination of crystals with light at T=77 K. The possible model of photostimulated processes in LiH(D):Ru crystals is presented.

The formation of two independent paramagnetic centres Ru(JT) and Ru(A) was detected by the EPR method LiH and LiD single crystals doped with ruthenium, after illumination with visible light at T=77 K. Both centres were assigned to Ru+ with low-spin 4d7 configuration. Ru(JT) centres exhibit a quasidynamical Jahn-Teller effect. The values of tunnelling splitting 3 Gamma and random-strain splitting delta were estimated to be 24 cm-1 and 6.0 cm-1, respectively. The Ru(A) centre was found to have tetragonal symmetry with the unpaired electron in a 4d(3z2-r2) orbital.