Yatsuhisa Nagano

Critically evaluated thermochemical properties of polycyclic aromatic hydrocarbons

Experimental thermochemical properties of benzene, toluene, and 63 polycyclic aromatic hydrocarbons, published within the period 1878–2008 (over 350 references), are reported. Available experimental data for the enthalpies of combustion used to calculate enthalpies of formation in the condensed state, combined with sublimation, vaporization, and fusion enthalpies, are critically evaluated. Whenever possible, recommended values for these thermochemical properties and for the enthalpies of formation in the gas state at T=298.15K are provided.

Laser photoelectron spectroscopic determination of electronic states of Fe atoms produced in multiphoton dissociation of Fe(CO)5 in the gas phase

Multiphoton ionization (MPI) ion–current and photoelectron measurements were carried out for Fe(CO)5 in the gas phase with a visible dye laser in the wavelength region 446–452 nm. This wavelength region was chosen for the reason that the MPI ion–current spectrum shows a typical complicated pattern consisting of many atomic lines. At least 35 sharp ion–current peaks have been detected under moderate laser power conditions in the present work. From the observed photoelectron spectra, all these ion–current peaks have been successfully assigned to three‐photon ionizations of Fe atoms which are produced in the five low‐lying electronic states in the photodissociation of Fe(CO)5. In this paper, we want to report photoelectron spectroscopic evidences for the production of the excited state Fe atoms in the laser photolysis of Fe(CO)5. Furthermore we want to emphasize the potentiality of laser photoelectron spectroscopy for identification of various nonradiative electronic states of transient species.

Mixing Schemes in a Urea-H2O System : A Differential Approach in Solution Thermodynamics

The excess partial molar enthalpies of urea (UR), H U R (E ), were experimentally determined in UR-H 2O at 25 degrees C. The H U R (E ) data were determined accurately and in small increments in the mole fraction of UR, x U R , up to x U R approximately 0.22. Hence it was possible to evaluate one more x U R -derivative graphically without resorting to any fitting function, and the model-free UR-UR enthalpic interaction, H U R- U R (E ), was calculated. Using previous data for the excess chemical potential, mu U R (E ), the entropy analogue, S U R- U R (E ), was also calculated. The x U R -dependences of both H U R- U R (E ) and S U R- U R (E ) indicate that there is a boundary at x U R approximately 0.09 at which the aggregation nature of urea changes. From the results of our earlier works, we suggest that a few UR molecules aggregate at x U R approximately 0.09, while the integrity of H 2O is retained at least up to x U R approximately 0.20. Together with the findings from our previous studies, we suggest that in the concentration range x U R < 0.22, UR or its aggregate form hydrogen bonds to the H 2O network, reducing the degree of fluctuation characteristic to liquid H 2O. However, up to at least x U R = 0.20 the hydrogen bond network remains intact. Above x U R approximately 0.22, the integrity of H 2O is likely be lost. Thus, in discussing the effect of urea on H 2O and in relating it to the structure and function of biopolymers in aqueous solutions, the concentration region in question must be specified.

Stoichiometry and phase behavior of carbon tetrachloride solvates of C60

Abstract Two solvated crystals of C 60 were formed from CCl 4 solutions. It was found that the cubic solvated crystal is composed of a C 60 (CCl 4 ) 13 formula unit while the hexagonal crystal has a C 60 (CCl 4 ) 2 unit. These solvates have phase behavior comparable with that of cyclohexane solvates of C 60 , being closely related to binary sphere mixtures with a characteristic diameter ratio of 0 .58. The present calorimetric study strongly suggests that the C 60 (CCl 4 ) 13 crystal has an AB 13 -type structure, in which icosahedron clusters of CCl 4 like those in the cyclohexane analogue are formed.

Photoelectron spectra and angular distribution in reson three-photon ionization of atomic iron: J dependence

Abstract Kenetic energies and angular distributions of photoelectrons emitted by three-photon ionization fo atomic iron through two-photon resonant state e 7 D J and e 5 D J , were measured, by using visible lasers. J -resolved photoelectron bands attributab to the a 6 D J and a 4 F j ionic states are reported.

Micro-combustion Calorimetry Aiming At 1 mg Samples

A micro-combustion calorimeter was developed. The small energy equivalent (ca. 68 JK−1) of this calorimeter makes it possible to measure combustion energies of very small samples. The energy equivalent was determined by burning 2 mg of benzoic acid. The standard deviation of the mean energy equivalent was reduced to 0.014% in 5 experiments. The standard massic energy of combustion of salicylic acid and the standard deviation of the mean were determined to be −21871±5 J g−1, which agrees well with the literature values. The standard molar enthalpy of formation of salicylic acid was derived as −591.2±1.7 kJ mol−1.

CO2 absorption in C60 solid

Abstract A large amount of CO 2 absorption in CO 60 solid was found under a supercritical CO 2 treatment. Absorption kinetics show that the process is significantly slower than normal physical adsorptions and is accelerated with increasing temperature. The CO 2 infrared absorptions are observed at 2329 and 651 cm −1 , suggesting a strong interaction between CO 2 and C 60 . DSC thermograms show a remarkable effect of the CO 2 absorption on the orientational phase transition at 250 K of C 60 crystals.

Stoichiometry and thermodynamic property of massively cyclohexane-solvated C60

Abstract A cyclohexane-solvated C60 compound was calorimetrically found to form two stoichiometric crystalline phases, C60(C6CH12)13.7 and C60(C6H12)2). The former phase has a novel structure AB13 composed of binary spheres. The solubility of C60(C6H12)13.7 was measured at various temperatures. C60(C6H12)13.7 is an incongruently melting compound with a peritectic point at T = 77°C.

Air oxidation of carbon soot generated by laser ablation

Abstract Carbon soot was generated by laser ablation under oxygen-free and regulated-temperature conditions at 300 K and 1500 K. The soot was significantly oxidised by being exposed to air in darkness. The degree of oxidation was determined to be 0.038±0.012 and 0.093±0.009 for the high temperature (HT) soot and the low temperature (LT) soot, respectively, on the basis of elemental analysis, XPS and Karl-Fischer titration. Water physically absorbs on the soot in proportion to the degree of oxidation. TG, TPD and 13C-NMR revealed that there were at least 2 kinds of oxidised states. One of them mainly contributes to CO and CO2 emissions at 420–970 K, while another contributes to CO emission above 770 K. The former is a dominant oxide in the LT soot. On the basis of FT-IR and 13C-NMR spectra, carbonyl groups were confirmed to be one of the major oxidised species in the soot. FT-IR and acid-base titration revealed that the LT soot adsorbed more CO2 than the HT soot did. The adsorbed CO2 contributes to the acidic property of the soot. The soot is paramagnetic as well as conductive. C1s and Auger photoelectron spectra of the soot were neither graphite-like nor diamond-like. The air oxidation is discussed in relation to unique structures and formation mechanisms of the soot.

C60CCl4 solvate: an AB13 type binary crystal

The density of the cubic C60CCl4 solvated crystal was measured to be 1.77 ± 0.01 g cm−3 at 20°C by the buoyancy method. The density and lattice constant, a = 27.38 A, confirm that the crystal is composed of a C60(CCl4)13 formula unit. The AB13 type structure known in binary alloy and colloid systems is proposed for this solvated crystal.