Saturation of fullerite C60 with hydrogen: Adsorption crossover studies

Yagotintsev, K. A.; Legchenkova, Irina; Stetsenko, Yu. E.; Zinoviev, P. V.; Zoryansky, V. N.; Prokhvatilov, A. I.; Strzhemechny, M. A.

doi:10.1063/1.4758781

Cited by 11 publications

(15 citation statements)

References 23 publications

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“…The fact that the depth of the optically active layer in photoluminescence measurements and the powder dimensions were comparable ensured reliability of the common sample attribution for spectroscopic and x-ray findings. For reader's convenience we recall certain results obtained during saturation and subsequent x-ray measurements [30] of C 60 -H 2 samples. In Fig.…”

Section: Experimental Technique and Samplesmentioning

confidence: 99%

“…By comparing the runs for saturation temperatures sat = 150 T and 200 °C, we conclude that for the lower saturation temperature the maximum possible saturation level has not been reached while for the higher saturation temperature after 50 h hydrogen penetrated virtually to all O-voids. As the relevant analysis shows [30], when saturated at 250 °C and higher, carbon atoms of fullerite start bonding chemically with hydrogen to form compounds C 60 H x . Leaning on this finding, in all luminescence measurements we dealt only with C 60 samples, intercalated to various saturation levels at temperatures below 250 °C.…”

Section: Experimental Technique and Samplesmentioning

confidence: 99%

“…A detailed description of the process of stuffing C 60 single crystals with hydrogen as well as the relevant characterization of samples can be found elsewhere [30]. Luminescence studies of C 60 intercalated with molecular hydrogen were carried out with a setup which allowed us to register emission from sources with low quantum output over a wide temperature range (10-300 K).…”

Section: Experimental Technique and Samplesmentioning

confidence: 99%

“…We note here that the samples for the x-ray studies carried out simultaneously [30] were prepared by crushing C 60 single crystals to a powder with an average size of below ∼ 20 μm. The fact that the depth of the optically active layer in photoluminescence measurements and the powder dimensions were comparable ensured reliability of the common sample attribution for spectroscopic and x-ray findings.…”

Section: Experimental Technique and Samplesmentioning

confidence: 99%

“…The relevant results of those x-ray studies, of importance in themselves, are published independently [30].…”

Section: Introductionmentioning

confidence: 99%

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Orientational glassification in fullerite C60 saturated with H2: Photoluminescence studies

Zinoviev

Zoryansky

Silaeva

et al. 2012

Low Temperature Physics

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Using one-photon excitation we studied photoluminescence of C 60 saturated with molecular hydrogen over a temperature range 10 to 230 K. Saturation of samples was done at a pressure of 30 atm and at temperatures low enough (T < 250 °C) to exclude chemical sorption. The samples were saturated during periods of varied duration τ to reach different occupancy levels. To check reliability of our luminescence results and interpretation, our spectra for pure C 60 were compared with data known in the art, demonstrating good compatibility. The luminescence spectra were attributed according to the approach of Akimoto and Kan , no by separating total spectra in two components of different origin. The A-type spectra, which are associated with exciton transport to deep traps, above 70 K become prevail over the B-type emission. Until saturation times did not exceed a certain value (for one, 50 h for a saturation temperature of 200 °C) the integrated intensity I as a function of the temperature T of luminescence measurements, I(T), remained at a constant level up to the orientational vitrification point of about 100 K and then went rather steeply down with increasing T. However, at longer τ the intensity I(Τ) persisted in constancy to higher T (the higher, the longer τ) and then dropped with increasing T. This finding made us to reexamine more closely the lattice parameter vs saturation time dependence for saturation temperatures 200 and 230 °C. As a result, additional evidence allowed us to infer that after completion of the single-molecule filling of O-voids (specifically, after roughly 50 h for T sat = 200 °C) a slower process of double filling sets in. Double filling entails an anisotropic deformation of the octahedral cage, which modifies rotational dynamics stronger than single filling. Further, we argue that singlet exciton transport to traps (which is responsible for the A-type emission) can be crucially hampered by rotational jumps of one of the molecules over which a travelling exciton is spread. Such jumps break coherence and the exciton stops thereby increasing the probability of emissionless deactivation. If so, then the temperature, at which the rotational jumps occur sufficiently frequently, may be by inference considered the unfreezing point for the orientational glass state (essentially coinciding with the inverse critical point T g where the rotational system freezes into the orientational glass). This treatment of T g differs from that existing in the art according to which the glass state is destroyed owing to the increased density of phonon states. Keeping to our reasoning, we conclude that the orientational glass state does not disappear but, instead, is conserved almost unchanged under one-molecule feeling and persists to appreciably higher temperatures in the case of double filling, which affects exciton dynamics stronger.

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Section: Experimental Technique and Samplesmentioning

confidence: 99%

Section: Experimental Technique and Samplesmentioning

confidence: 99%

Section: Experimental Technique and Samplesmentioning

confidence: 99%

Section: Experimental Technique and Samplesmentioning

confidence: 99%

“…The relevant results of those x-ray studies, of importance in themselves, are published independently [30].…”

Section: Introductionmentioning

confidence: 99%

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Orientational glassification in fullerite C60 saturated with H2: Photoluminescence studies

Zinoviev

Zoryansky

Silaeva

et al. 2012

Low Temperature Physics

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Thermally Activated D₂ Emission upon Decomposition of Thin Deuterofullerene Films on Au(111)

et al. 2014

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We have studied the formation and thermal properties of thin, deuterofullerene-containing films on Au(111) under ultrahigh vacuum conditions. The films were prepared in situ by exposure of predeposited C 60 layers to a flux of atomic deuterium. With increasing deuterium dose, a D + C 60 → C 60 D x reaction front propagates through the fullerene film toward the gold surface. Heating the resulting deuterofullerene-containing films to >600 K leads to desorption of predominantly C 60 and C 60 D x . Interestingly, some D 2 is also evolved while a significant fraction of the carbon initially deposited is left on the surface as nondesorbable residue. This is in contrast to analogous deuterofullerene-containing films prepared on graphite, which sublime completely but do not measurably evolve D 2 , suggesting that the gold surface can act as a catalyst for D 2 formation. To explore this further, we have systematically studied (i) the thermal properties of C 60 /Au(111) reference films, (ii) the reaction of C 60 /Au(111) films with D atoms, and (iii) the heatinginduced degradation of deuterofullerene-containing films on Au(111). In particular, we have recorded temperature-resolved mass spectra of the desorbing species (sublimation maps) as well as performed ultraviolet photoionization spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and scanning tunneling microscopy measurements of the surfaces at various stages of study. We infer that heating deuterofullerene-containing films generates mobile deuterium atoms which can recombine to form molecular deuterium either at the gold surface or on fullerene oligomers in direct contact with it.

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Effect of nitrogen sorption mechanisms on the properties of fullerite C60 over a wide range of temperatures

Legchenkova

Yagotintsev

Galtsov

et al. 2014

Low Temperature Physics

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X-ray diffractometry is used to study the effect of the adsorption of nitrogen at a pressure of 30 atm and temperatures of 200–550 °C on the structural and thermodynamic properties of fullerite C60. The sorption kinetics of nitrogen at different temperatures are studied, and the lattice parameter is plotted as a function of the time for fullerite to saturate with nitrogen. The sorption mechanism is found to change with increasing saturation temperature. The diffusive filling of lattice octahedral voids by nitrogen atoms at temperatures below 450 °C is supplanted at higher temperatures by a chemical interaction of nitrogen with fullerite molecules leading to the formation of a new molecular compound, fullerite nitride C60Nx. The transition from physisorption to chemisorption of nitrogen by fullerite (the adsorption crossover) takes place at saturation temperatures of 450 > T > 400 °C. When C60 molecules are nitrogenated, the volume of the cubic cell increases dramatically, while the intensity of the x-ray reflections decreases and their width increases rapidly. The limiting distortions of the fcc lattice are determined, as well as the characteristic times for diffusional filling of the lattice voids and for nitrogenation, respectively, during physical and chemical sorption of nitrogen. Nitrogenation of fullerite molecules leads to a significant reduction in thermal expansion of the crystalline material, and suppresses both the orientational phase transition and formation of the glassy state.

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Saturation of fullerite C60 with hydrogen: Adsorption crossover studies

Cited by 11 publications

References 23 publications

Orientational glassification in fullerite C60 saturated with H2: Photoluminescence studies

Orientational glassification in fullerite C60 saturated with H2: Photoluminescence studies

Thermally Activated D₂ Emission upon Decomposition of Thin Deuterofullerene Films on Au(111)

Effect of nitrogen sorption mechanisms on the properties of fullerite C60 over a wide range of temperatures

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Saturation of fullerite C60 with hydrogen: Adsorption crossover studies

Cited by 11 publications

References 23 publications

Orientational glassification in fullerite C60 saturated with H2: Photoluminescence studies

Orientational glassification in fullerite C60 saturated with H2: Photoluminescence studies

Thermally Activated D2 Emission upon Decomposition of Thin Deuterofullerene Films on Au(111)

Effect of nitrogen sorption mechanisms on the properties of fullerite C60 over a wide range of temperatures

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Thermally Activated D₂ Emission upon Decomposition of Thin Deuterofullerene Films on Au(111)