Физика низких температур, 2010, № 05http://dspace.nbuv.gov.ua:80/handle/123456789/1151532024-03-28T18:45:28Z2024-03-28T18:45:28ZUnveiled optical properties of tetrapyrollic pigments in cryogenic environmentsCrépin, C.Shafizadeh, N.Chin, W.Galaup, J.-P.McCaffrey, J.G.Arabei, S.M.http://dspace.nbuv.gov.ua:80/handle/123456789/1170462017-05-20T00:03:06Z2010-01-01T00:00:00ZUnveiled optical properties of tetrapyrollic pigments in cryogenic environments
Crépin, C.; Shafizadeh, N.; Chin, W.; Galaup, J.-P.; McCaffrey, J.G.; Arabei, S.M.
An unexpected phenomenon was revealed in the laser induced fluorescence spectra of free-base (H₂Pc) and zinc (ZnPc) phthalocyanines trapped in rare gas and nitrogen matrices under a moderate increase in the laser intensity. In all matrices the intensity of an emission band near 755 nm increased drastically when pumping the S₁←S₀ transition. This observation was assigned to stimulated emission in a four-level scheme involving a vibronic transition from the lowest electronic state to a vibrational level of the ground state. In the present work, we expose new similar results obtained with porphyrin molecules, i.e. tetra-benzoporphin (TBP). With free-base H₂TBP, stimulated emission was observed in Ar or N₂ matrices, but not in Xe matrices. A possible reason could be a fast inter-system crossing rate due to the heavy atom effect induced by Xe. We also report the observation of persistent burnt spectral holes, although the low efficiency of this process is not competitive with stimulated emission and no decrease of the stimulated emission with time was observed. With ZnTBP, no stimulated emission could be recorded; however the appearance of rather strong phosphorescence was noticed. Similar studies focusing on the stimulated emission phenomenon is that they should allow new insights into site effects and site selectivity.
2010-01-01T00:00:00ZSingle-molecule probing of incommensurate biphenylPärs, M.Palm, V.Kikas, J.http://dspace.nbuv.gov.ua:80/handle/123456789/1170452017-05-20T00:03:05Z2010-01-01T00:00:00ZSingle-molecule probing of incommensurate biphenyl
Pärs, M.; Palm, V.; Kikas, J.
Our data on the distribution of purely-electronic linewidths of terrylene single molecules in incommensurate biphenyl crystals are compared with the data of other groups for different low-temperature organic solid hosts and with results of numerical simulations. The first two moments of the distributions measured within a narrow temperature interval have been used to calculate a single dimensionless parameter characterizing each of the respective hosts — the variation coefficient. It appears that different amorphous hosts have similar values of this coefficient, but the value obtained for the incommensurate crystal of biphenyl is significantly different. One can conclude that the remarkable single-molecule line broadening in biphenyl at 1.8 K cannot be solely explained by the interaction with two-level systems, which is considered to cause the broadening in amorphous hosts.
2010-01-01T00:00:00ZStudy of the cluster formation in low-temperature systems. Spectral manifestation of resonance dipole–dipole interactions between nondipole polyatomic moleculesCherevatova, A.N.Bocharov, V.N.Kolomiitsova, T.D.Shchepkin, D.N.Tokhadze, K.G.http://dspace.nbuv.gov.ua:80/handle/123456789/1170442017-05-20T00:03:05Z2010-01-01T00:00:00ZStudy of the cluster formation in low-temperature systems. Spectral manifestation of resonance dipole–dipole interactions between nondipole polyatomic molecules
Cherevatova, A.N.; Bocharov, V.N.; Kolomiitsova, T.D.; Shchepkin, D.N.; Tokhadze, K.G.
Resonance dipole–dipole interactions are shown to strongly manifest themselves in fundamental and overtone band shapes of low-temperature systems, consisting of polar and nonpolar molecules as well with a relatively large first derivatives (P′ > 0.3 D) of the dipole moment. The rough model on the basis of the interaction between two non-degenerate, doubly degenerate, and triply degenerate oscillators was developed to study pairs of interacting molecules and clusters in low-temperature condensed systems. The concentration dependences of second- and third-order spectral band moments permitted the number of molecules in clusters to be estimated.
2010-01-01T00:00:00ZPhonons of solid phases (α, β, δ, ε) of carbon monoxide by optical studiesSerdyukov, A.Vetter, M.Brodyanski, A.Jodl, H.J.http://dspace.nbuv.gov.ua:80/handle/123456789/1170432017-05-20T00:02:59Z2010-01-01T00:00:00ZPhonons of solid phases (α, β, δ, ε) of carbon monoxide by optical studies
Serdyukov, A.; Vetter, M.; Brodyanski, A.; Jodl, H.J.
The phase diagram of solid carbon monoxide was investigated in the pressure range 0–10 GPa and temperature range 30–300 K by infrared and Raman spectroscopy. The tentative phase diagram known from literature was expanded and specified in details. The δ-phase region is divided into two subphases — δrot and δloc that is similar to the one in solid nitrogen. The pressure-temperature behavior of the elementary and combined excitations was also followed up. The vibron overtone region was carefully investigated by FTIR spectroscopy as a function of temperature at different pressures, whereas the fundamental one — by Raman spectroscopy. The features of the IR-active phonon sideband to the vibron overtone were investigated in details in the whole pressure-temperature region. The lattice-phonon spectra were studied by Raman spectroscopy as a function of pressure (at lowest temperature) and by IR spectroscopy as a function of temperature at saturated vapor pressure.
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