Slow cross-symmetry phase relaxation in complex collisions

We discuss the effect of slow phase relaxation and the spin off-diagonal S-matrix correlations on the cross-section energy oscillations and the time evolution of the highly excited intermediate systems formed in complex collisions. Such deformed intermediate complexes with strongly overlapping resonances can be formed in heavy-ion collisions, bimolecular chemical reactions, and atomic cluster collisions. The effects of quasiperiodic energy dependence of the cross sections, coherent rotation of the hyperdeformed similar or equal to(3 : 1) intermediate complex, Schrodinger cat states, and quantum-classical transition are studied for Mg-24 + Si-28 heavy-ion scattering.

Effect of phase relaxation on quantum superpositions in complex collisions

We study the effect of phase relaxation on coherent superpositions of rotating clockwise and anticlockwise wave packets in the regime of strongly overlapping resonances of the intermediate complex. Such highly excited deformed complexes may be created in binary collisions of heavy ions, molecules, and atomic clusters. It is shown that phase relaxation leads to a reduction of the interference fringes, thus mimicking the effect of decoherence. This reduction is crucial for the determination of the phase-relaxation width from the data on the excitation function oscillations in heavy-ion collisions and bimolecular chemical reactions. The difference between the effects of phase relaxation and decoherence is discussed.

Thermochemical and thermal analysis on N-(p-methylphenyl)-N '-(2-pyridyl)urea

Low temperature heat capacities of N-(p-methylphenyl)-N'-(2-pyridyl)urea were determined by adiabatic calorimetry method in the temperature range from 80 to 370 K. It was found that there was not any heat anomaly in this temperature region. Based on the experimental data, some thermodynamic function results were obtained. Thermal stability and decomposition characteristics analysis of N-(p-methylphenyl)-N'-(2-pyridyl)urea were carried out by DSC and TG. The results indicated that N-(p-methylphenyl)-N'-(2-pyridyl)urea started to melt at ca. 426 K (153degreesC) and the melting peak located at 447.01 K (173.86degreesC). The melting enthalpy was 204.445 kJ mol(-1) (899.6 J g(-1)). The decomposition peak of N-(p-methylphenyl)-N'-(2-pyridyl)urea was found at 499.26 K (226.11degreesC) from DSC curve. This result was similar with that from TG and DTG experiment, in which the mass loss peak was determined as 500.4 K (227.2degreesC).

Heat capacities and thermodynamic properties of chrysanthemic acid

The heat capacities of chrysanthemic acid in the temperature range from 80 to 400 K were measured with a precise automatic adiabatic calorimeter. The chrysanthemic acid sample was prepared with the purity of 0.9855 mole fraction. A solid-liquid fusion phase transition was observed in the experimental temperature range. The melting point, T-m, enthalpy and entropy of fusion, Delta(fus)H(m), Delta(fus)S(m), were determined to be 390.741 +/- 0.002 K, 14.51 +/- 0.13 kJ mol(-1), 37.13 +/- 0.34 J mol(-1) K-1, respectively. The thermodynamic functions of chrysanthemic acid, H-(T)-H-(298.15), S-(T)-S-(298.15) and G((T))-G((298.15)) were reported with a temperature interval of 5 K. The TG analysis under the heating rate of 10 K min(-1) confirmed that the thermal decomposition of the sample starts at ca. 410 K and terminates at ca. 471 K. The maximum decomposition rate was obtained at 466 K. The purity of the sample was determined by a fractional melting method.

Low-temperature heat capacities and standard molar enthalpy of formation of aspirin

Molar heat capacities (C-p,C-m) of aspirin were precisely measured with a small sample precision automated adiabatic calorimeter over the temperature range from 78 to 383 K. No phase transition was observed in this temperature region. The polynomial function of Cp, vs. T was established in the light of the low-temperature heat capacity measurements and least square fitting method. The corresponding function is as follows: for 78 Kless than or equal toTless than or equal to383 K, C-p,C-m/J mol(-1) K-1=19.086X(4)+15.951X(3)-5.2548X(2)+90.192X+176.65, [X=(T-230.50/152.5)]. The thermodynamic functions on the base of the reference temperature of 298.15 K, {DeltaH(T)-DeltaH(298.15)} and {S-T-S-298.15}, were derived.

Heat capacity and thermodynamic properties of pyrimethanil myristic salt (C26H41N3O2)

Pyrimethanil myristic salt was synthesized and its heat capacities were measured with an automated adiabatic calorimeter over the temperature range from T = (79 to 360) K. The melting point, molar enthalpy, Delta(fus)H(m) and entropy, Delta(fus)S(m), of fusion of this compound were determined to be (321.84 +/- 0.05) K, (56.53 +/- 0.03) kJ . mol(-1) and (175.64 +/- 0.05) J . mol(-1) . K-1, respectively. The purity of the compound was calculated to be 98.99 mol% by using the fractional melting technique. The thermodynamic functions relative to the reference temperature, T = 298.15 K, were calculated based on the heat capacity measurements in the temperature ranges from T = (80 to 360) K. The TG-DTG results demonstrate that the mass loss of the sample takes place in one step with the maximum rate at T = 500 K, which was caused by evaporation of the sample. (C) 2004 Elsevier Ltd. All rights reserved.

Heat capacity and thermodynamic properties of crystalline ornidazole (C7H10ClN3O3)

The molar heat capacities of 1-(2-hydroxy-3-chloropropyl)-2-methyl-5-nitroimidazole (Ornidazole) (C7H10CIN3O3) with purity of 99.72mol% were measured with an adiabatic calorimeter in the temperature range between 79 and 380K. The melting-point temperature, molar enthalpy Delta(fus)H(m), and entropy, Delta(fus)S(m), of fusion of this compound were determined to be 358.59 +/- 0.04K, 21.38 +/- 0.02 kJ mol(-1) and 59.61 +/- 0.05 J K-1 mol(-1), respectively, from fractional melting experiments. The thermodynamic function data relative to the reference temperature (298.15 K) were calculated based on the heat capacities measurements in the temperature range from 80 to 380 K. The thermal stability of the compound was further investigated by DSC and TG. From the DSC curve an intensive exothermic peak assigned to the thermal decomposition of the compound was observed in the range of 445-590 K with the peak temperature of 505 K. Subsequently, a slow exothermic effect appears when the temperature is higher than 590 K, which is probably due to the further decomposition of the compound. The TG curve indicates the mass loss of the sample starts at about 440K, which corresponds to the decomposition of the sample. (C) 2003 Elsevier B.V. All rights reserved.

Thermodynamic studies of monuron

Monuron (C9H11ClN2O; N,N-dimethyl-N'-(4-chlorophenyl) urea, CAS 150-68-5) was synthesized and the heat capacities of the compound were measured in the temperature range from 79 to 385 K with a high precision automated adiabatic calorimeter. No phase transition or thermal anomaly was observed in this range. The enthalpy and entropy data of the compound relative to the reference temperature 298.15 K were derived based on the heat capacity data. The thermodynamic properties of the compound were further investigated through DSC and TG analysis. The melting point, the molar enthalpy, and entropy of fusion were determined to be 447.6 +/- 0.1 K, 29.3 +/- 0.2 kJ mol(-1), and 65.4 J K-1 mol(-1), respectively. (C) 2004 Elsevier B.V. All rights reserved.

Heat capacity and enthalpy of fusion of penconazole (C13H15C12N3)

Low-temperature heat capacities of penconazole (C13H15Cl2N3) were precisely measured with an automated adiabatic calorimeter over the temperature rang from 78 to 364 K. The sample was observed to melt at 332.38 +/- 0.06 K. The molar enthalpy and entropy of fusion of the compound were determined to be 33580 +/- 11 J mol(-1), 101.03 +/- 0.02 J mol(-1) K-1, respectively. Further research of the melting process for this compound was carried out by means of differential scanning calorimetry (DSC) technique. The result was in agreement with that obtained from the measurements of heat capacities. (C) 2003 Elsevier B.V. All rights reserved.

Thermodynamic study of ibuprofen by adiabatic calorimetry and thermal analysis

Molar heat capacities of ibuprofen were precisely measured with a small sample precision automated adiabatic calorimeter over the temperature range from 80 to 400 K. The polynomial functions of C-p,C-m (J K-1 mol(-1)) versus T were established on the heat capacity measurements by means of the least fitting square method. The functions are as follows: for solid ibuprofen, at the temperature range of 79.105 K less than or equal to T less than or equal to 333.297 K, C-p,C-m = 144.27 + 77.046X + 3.5171X(2) + 10.925X(3) + 11.224X(4), where X = (T - 206.201)/127.096; for liquid ibuprofen, at the temperature range of 353.406 K less than or equal to T less than or equal to 378.785 K, C-p,C-m = 325.79 + 8.9696X - 1.6073X(2) - 1.5145 X-3, where X = (T - 366.095)/12.690. A fusion transition at T = 348.02 K was found from the C-p-T curve. The molar enthalpy and entropy of the fusion transition were determined to be 26.65 kJ mol(-1) and 76.58 J mol(-1) K-1, respectively. The thermodynamic functions on the base of the reference temperature of 298.15 K, (H-T - H-298.15) and (S-T - S-298.15), were derived. Thermal characteristic of ibuprofen was studied by thermo-gravimetric analysis (TG-DTG) and differential scanning calorimeter (DSC). The temperature of fusion, the molar enthalpy and entropy of fusion obtained by DSC were well consistent with those obtained by adiabatic calorimeter. The evaporation process of ibuprofen was investigated further by TG and DTG, and the activation energy of the evaporation process was determined to be 80.3 +/- 1.4 kJ mol(-1). (C) 2003 Elsevier B.V. All rights reserved.