jeanflop/post_ocr_correction2 huggingface dataset:
satisfactory and yields a rather accurate simulation of the experimental energy level scheme. The mean deviation observed/calculated values amounts to 0.01 x crystal field strength. The expression for the latter is given by: with (B*)2 = £(Bj)2 (référence [1]). 9 / is the value of the electron angular momentum, fe is even and lower than 2x1, the B* are the crystal field parameters (cfp). For instance, the mean crystal field strengths of LaCl3: Nd3+, NdAlO3, NdOCl, Nd2O3, and Y2O3: Nd3+ are equal to 622, 1,508, 1,360, 1,841, and 2,516 cm−1 respectively, while parametric adjustments yield mean deviations equal to 7, 12, 17, 14, and 17 cm−1 respectively. Usually, one has to discard from the fitting procedure the 2H(2)11/2 levels, well isolated and located at about 15,000 cm−1 which come out of the calculation as a compactly squeezed set, miniature of the experimental energy level sequence. 2. EFFECTS OF THE COUPLING WITH THE TWIN LEVEL. — In reference [5], we stress the connection which always seems to exist between the contraction of the calculated 2H(2)11/2 levels and the coupling with the twin level situated above 30,000 cm−1. We also empirically demonstrate, with reference to experimental results, that the relative discrepancy: experimental/calculated values varies as B4/(B2 + B6), which means that the relative contraction increases when fourth order cfp increase but is attenuated if second and sixth order parameters are increased. Presently, we shall explain how the calculated contraction occurs inexorably for this level when the fourth order crystal field parameters display high values and quote the relation which is responsible for this contraction. Since the 2H(2)11/2 levels are well isolated, the diagonalization of a small 24x24 interaction matrix taking into account electrostatic and crystal field interaction, within the sub-levels of 2H(2)11/2 and 3K(2)8. TABLE Effect of coupling with the twin level on the crystal field interaction within the sub-levels of 2H(2)11/2 and 3K(2)8. A and S are defined in (7) and (8) respectively, A/S gives roughly the strengthening or weakening of crystal field effect on the 2H(2)11/2 and 3K(2)8 levels due to the coupling. Influence du couplage avec le niveau frère
values varies as B4/(B2 + B6), which means that the relative contraction increases when fourth order cfp increase but is attenuated if second and sixth order parameters are increased. Presently, we shall explain how the calculated contraction occurs inexorably for this level when the fourth order crystal field parameters display high values and quote the relation which is responsible for this contraction. Since the 2H(2)11/2 levels are well isolated, the diagonalization of a small 24x24 interaction matrix taking into account electrostatic and crystal field interaction, within the sub-levels of 2H(2)11/2 and 3K(2)8. TABLE Effect of coupling with the twin level on the crystal field interaction within the sub-levels of 2H(2)11/2 and 3K(2)8. A and S are defined in (7) and (8) respectively, A/S gives roughly the strengthening or weakening of crystal field effect on the 2H(2)11/2 and 3K(2)8 levels due to the coupling. Influence du couplage avec le niveau frère sur l'éclatement sous le champ cristallin des niveaux 2H(2)11/2 et 3K(2)8. A and S are defined in (1) and (8) respectively, A/S donne une idée du renforcement ou de l'affaiblissement de l'effet du champ cristallin sur les niveaux 2H(2)11/2 et 3K(2)8 du fait du couplage. Twin R.E. fc A SA/S 2H (Nd3+) 2 -3,941 2,152 -1.83 4 -764 6,453 -0.12 6 -1,753 956 -1.83 3K (Ho3+) 2 4,219 17,309 0.24 4 -746 23,955 -0.03 6 -4,250 2,370 -1.79 The electrostatic interaction is given by: where S, L, J, M and S', L', J', M' are the quantum numbers of the two interacting spectroscopic states, the En are Racah's parameters, and the an are reduced matrix elements listed in Nielson and Koster's tables [6]. Therefore, the electrostatic interaction is "diagonal" and displays constant values within the 2H(1) — 2H(1), 2H(2) — 2H(2) and 2H(1) 2H(2) blocks. We call these three values: The crystal field interaction is given by: The <ySL || Ufc || y'SL' > are reduced matrix elements for coupled states, they have been computed by Nielson and Koster and are listed in reference [6]. Within the two 2H(1) and 2H(2) blocks, the relevant reduced matrix elements are: With the
2H (Nd3+) 2 -3,941 2,152 -1.83 4 -764 6,453 -0.12 6 -1,753 956 -1.83 3K (Ho3+) 2 4,219 17,309 0.24 4 -746 23,955 -0.03 6 -4,250 2,370 -1.79 The electrostatic interaction is given by: where S, L, J, M and S', L', J', M' are the quantum numbers of the two interacting spectroscopic states, the En are Racah's parameters, and the an are reduced matrix elements listed in Nielson and Koster's tables [6]. Therefore, the electrostatic interaction is "diagonal" and displays constant values within the 2H(1) — 2H(1), 2H(2) — 2H(2) and 2H(1) 2H(2) blocks. We call these three values: The crystal field interaction is given by: The <ySL || Ufc || y'SL' > are reduced matrix elements for coupled states, they have been computed by Nielson and Koster and are listed in reference [6]. Within the two 2H(1) and 2H(2) blocks, the relevant reduced matrix elements are: With the hypothesis of a C2v site symmetry allowing only B4 non-zero parameters, a separate formal resolution of the interaction matrix is possible for each k value. e1, e2, and e12 display larger values than the crystal field interaction terms. Let us group in a term called C,ail the crystal field interaction (4), except the reduced matrix element, j stands for all the quantum numbers in (4). We can express the six lowest eigenvalues of the interaction matrix which are the energies of the 2H(2)11/2 levels as functions of increasing powers of Cj/(e1+e2): If expression (6) happens to be independent (or nearly independent) of C-, then the lowest set of levels is quasi-degenerate. From (6) we see that it occurs if: is small compared to: We have listed in the Table the values of S, A, and A/S for the 2H11/2 levels, and for fe = 2, 4, and 6. Whether A/S is lower, equal, or larger than 1 allows to appreciate if crystal field interaction will be weakened, unaffected or enhanced in 2H(2)11/2 as a result of coupling with the twin level. This is a property of Nielson and Koster's tables. For instance, we state that the contribution of the fourth
(4), except the reduced matrix element, j stands for all the quantum numbers in (4). We can express the six lowest eigenvalues of the interaction matrix which are the energies of the 2H(2)11/2 levels as functions of increasing powers of Cj/(e1+e2): If expression (6) happens to be independent (or nearly independent) of C-, then the lowest set of levels is quasi-degenerate. From (6) we see that it occurs if: is small compared to: We have listed in the Table the values of S, A, and A/S for the 2H11/2 levels, and for fe = 2, 4, and 6. Whether A/S is lower, equal, or larger than 1 allows to appreciate if crystal field interaction will be weakened, unaffected or enhanced in 2H(2)11/2 as a result of coupling with the twin level. This is a property of Nielson and Koster's tables. For instance, we state that the contribution of the fourth order cfp in 2H(2)11/2 is grossly divided by ten for all the Nd3+ compounds as a result of the coupling u12 with the twin level. The peculiar fact is that the experimental levels are spread out as if this reduction had not occurred. 3. THE 3K(2)8 LEVEL OF HO3+. — Crosswhite et al. [2] state in the case of Ho3+ doping a LaCl3 matrix, a 40% reduction of the calculated splitting (in a 192x192 dimensioned matrix) with respect to the experimentally observed levels. The phenomenon is enhanced in a small 34 x 34 matrix isolating the two sets of 3K8 levels. The lower set comes out of the diagonalization nearly degenerate, however large the value of the fourth order parameter, a fact which allows to suspect the same avatar as for the 2H(2)11/2 level of Nd3+. Therefore, we have also listed in the Table the values of S, A, and A/S for the 3K(2)8 level. As emphasized above for the neodymium level, the effect of the fourth order parameters greatly weakens as a result of the coupling. The same occurs, but to a lesser extent for the contribution of the second order parameters, whereas the effect of the sixth order
Crosswhite et al. [2] state in the case of Ho3+ doping a LaCl3 matrix, a 40% reduction of the calculated splitting (in a 192x192 dimensioned matrix) with respect to the experimentally observed levels. The phenomenon is enhanced in a small 34 x 34 matrix isolating the two sets of 3K8 levels. The lower set comes out of the diagonalization nearly degenerate, however large the value of the fourth order parameter, a fact which allows to suspect the same avatar as for the 2H(2)11/2 level of Nd3+. Therefore, we have also listed in the Table the values of S, A, and A/S for the 3K(2)8 level. As emphasized above for the neodymium level, the effect of the fourth order parameters greatly weakens as a result of the coupling. The same occurs, but to a lesser extent for the contribution of the second order parameters, whereas the effect of the sixth order parameters is enhanced by the coupling, but with an opposite sign. Crosswhite et al. [2] indeed point out that they succeed in adjusting the 3K(2) spectroscopic term by utilizing for this term only, sixth order cfp eight times larger and of opposite sign than assumed in the conventional theory. More recently, Crosswhite and Newman have improved the fit of the 3K(2)8 level by adding the contribution of Spin Correlated Crystal Field, involving a two-electron parametrization. Presently, we cannot clearly see the link between this parametric interpretation and our empirical observations. Note remise le 12 octobre 1988, acceptée le 18 novembre 1988. REFERENCES [1] M. FAUCHER, D. GARCIA and C. K. JØRGENSEN, Chem. Phys. Lett., 129, 1986, pp. 387-391. [2] H. M. CROSSWHITE, H. CROSSWHITE, N. EDELSTEIN and K. RAJNAK, J. Chem. Phys., 67, 1977, pp. 3002-3010. [3] E. ANTIC-FIDANCEV, M. LEMAITRE-BLAISE, L. BEAURY, G. TESTE DE SAGEY and P. CARO, J. Chem. Phys., 73, 1980, pp. 4613-4618. C. R. Acad. Sci. Paris, t. 307, Série II, p. 2015-2019, 1988 2019 [4] J. ARIDE, Thèse de Doctorat es Sciences Physiques, Bordeaux-1, 1980, "Contribution à l'étude de la structure électronique 4f du néodyme dans différents environnements cristallins". [5] M. FAUCHER, D. GARCIA,
recently, Crosswhite and Newman have improved the fit of the 3K(2)8 level by adding the contribution of Spin Correlated Crystal Field, involving a two-electron parametrization. Presently, we cannot clearly see the link between this parametric interpretation and our empirical observations. Note remise le 12 octobre 1988, acceptée le 18 novembre 1988. REFERENCES [1] M. FAUCHER, D. GARCIA and C. K. JØRGENSEN, Chem. Phys. Lett., 129, 1986, pp. 387-391. [2] H. M. CROSSWHITE, H. CROSSWHITE, N. EDELSTEIN and K. RAJNAK, J. Chem. Phys., 67, 1977, pp. 3002-3010. [3] E. ANTIC-FIDANCEV, M. LEMAITRE-BLAISE, L. BEAURY, G. TESTE DE SAGEY and P. CARO, J. Chem. Phys., 73, 1980, pp. 4613-4618. C. R. Acad. Sci. Paris, t. 307, Série II, p. 2015-2019, 1988 2019 [4] J. ARIDE, Thèse de Doctorat es Sciences Physiques, Bordeaux-1, 1980, "Contribution à l'étude de la structure électronique 4f du néodyme dans différents environnements cristallins". [5] M. FAUCHER, D. GARCIA, P. CARO, J. DEROUET and P. PORCHER, J. Phys. (to be published). [6] C. W. NIELSON and G. F. KOSTER, Spectroscopic Coefficients for the p", d" and f" Configurations, M.I.T. Press, 1963. [7] H. CROSSWHITE and D. J. NEWMAN, J. Chem. Phys., 81, 1984, pp. 4959-4962. Laboratoire des Éléments de Transition dans les Solides, 1, place Aristide-Briand, 92195 Meudon Cedex. C. R. Acad. Sci. Paris, t. 307, Série II, p. 2021-2026, 1988 2021 Chimie minérale/Inorganic Chemistry Synthèse du nitrate de cérium (III) ammoniacal par réduction du nitrate de cérium (IV) ammoniacal par l'ammoniac anhydre Guy BOURLEAUX, Pierre COLOMBET, Jean ROUXEL, Peter S. GRADEFF et Heiko MAUERMANN Résumé — La réduction du nitrate cérique ammoniacal (NH4)2Ce(N03)6 par l'ammoniac anhydre a été étudiée. La réaction conduit à la formation d'un nitrate céreux ammoniacal, de formule (NH4)2Ce(N03)5(NH3);c avec x = 2,5 dans les conditions opératoires utilisées. Il s'agit d'une voie de synthèse de sels anhydres de cérium (III) facile à mettre en œuvre et pouvant éventuellement conduire par la suite à la préparation de dérivés organiques du cérium trivalent. Synthesis of cerous ammonium nitrate using CAN and anhydrous ammonia as a reducing agent Abstract — The reduction of ceric ammonium nitrate (CAN) by
Transition dans les Solides, 1, place Aristide-Briand, 92195 Meudon Cedex. C. R. Acad. Sci. Paris, t. 307, Série II, p. 2021-2026, 1988 2021 Chimie minérale/Inorganic Chemistry Synthèse du nitrate de cérium (III) ammoniacal par réduction du nitrate de cérium (IV) ammoniacal par l'ammoniac anhydre Guy BOURLEAUX, Pierre COLOMBET, Jean ROUXEL, Peter S. GRADEFF et Heiko MAUERMANN Résumé — La réduction du nitrate cérique ammoniacal (NH4)2Ce(N03)6 par l'ammoniac anhydre a été étudiée. La réaction conduit à la formation d'un nitrate céreux ammoniacal, de formule (NH4)2Ce(N03)5(NH3);c avec x = 2,5 dans les conditions opératoires utilisées. Il s'agit d'une voie de synthèse de sels anhydres de cérium (III) facile à mettre en œuvre et pouvant éventuellement conduire par la suite à la préparation de dérivés organiques du cérium trivalent. Synthesis of cerous ammonium nitrate using CAN and anhydrous ammonia as a reducing agent Abstract — The reduction of ceric ammonium nitrate (CAN) by anhydrous ammonia has been studied. The reaction yields cerous ammonium nitrate complex which can be formulated as (NH3)2Ce(N03)5(NH3)x with x = 2.5, but x can be more or less dependent on the drying conditions. This is an easy method to prepare an anhydrous Ce (III) salt, suitable for synthesis of organocerium (III) derivatives. Abridged English Version — Ceric ammonium nitrate (CAN) has been in use mostly as a reagent for oxidations [1], [2], [3]. Recently, it has been proposed as a starting material for organocerium (IV) derivatives [4]. CAN, which is in fact hydrated, can be dried under vacuum at 100-120°C without decomposition. This is not usually the case for the cerous double nitrates [7]. However, it appears that there is an exception concerning a previously reported Ce (III) tetrahydrate which seems to yield cerous ammonium nitrate, (NH4)2Ce(N03)5, when dried [8]. We have considered the use of anhydrous CAN as a source of anhydrous Ce (III) nitrate. We are describing here the use of ammonia, liquid or gas, in the reduction of CAN and the characterization of the resulting Ce (III) anhydrous species. The starting, as well as the final materials, were handled in a nitrogen-filled glove-box (<10 ppm H2O).
organocerium (III) derivatives. Abridged English Version — Ceric ammonium nitrate (CAN) has been in use mostly as a reagent for oxidations [1], [2], [3]. Recently, it has been proposed as a starting material for organocerium (IV) derivatives [4]. CAN, which is in fact hydrated, can be dried under vacuum at 100-120°C without decomposition. This is not usually the case for the cerous double nitrates [7]. However, it appears that there is an exception concerning a previously reported Ce (III) tetrahydrate which seems to yield cerous ammonium nitrate, (NH4)2Ce(N03)5, when dried [8]. We have considered the use of anhydrous CAN as a source of anhydrous Ce (III) nitrate. We are describing here the use of ammonia, liquid or gas, in the reduction of CAN and the characterization of the resulting Ce (III) anhydrous species. The starting, as well as the final materials, were handled in a nitrogen-filled glove-box (<10 ppm H2O). The ammonia (99.99%) was first dried over sodium then transferred to a pyrex h-cell tube containing previously dried CAN obtained from Rhône-Poulenc Inc. The tube was subsequently sealed to allow the reaction to proceed at room temperature. Alternatively, ammonia gas can be bubbled into a solution or suspension of CAN into an inert solvent. The progress of the reaction is followed up by the disappearance of the orange color. The completion of the reduction was confirmed by a test with N-phenylphenylamine sulfate added to a sample acidified with glacial acetic acid. The reduced CAN is an off-white solid containing coordinated free ammonia. It is soluble in liquid ammonia. In air and at room temperature, the product is slowly oxidized to CeO2. At 100°C, the process takes one week. Upon addition of water, the complex appears insoluble, because of instant formation of Ce-hydroxide. A sample of reduced CAN was analysed using X-ray diffraction (Debye-camera, CuKα radiation, calibrated with Si as a standard) showing the existence of both NH4NO3 and a compound which set of reflections is presented in Table. The magnetic susceptibility Note présentée par Jean ROUXEL. 0249-6305/88/03072021 S 2.00 © Académie des Sciences 2022 C. R. Acad. Sci. Paris, t.
into an inert solvent. The progress of the reaction is followed up by the disappearance of the orange color. The completion of the reduction was confirmed by a test with N-phenylphenylamine sulfate added to a sample acidified with glacial acetic acid. The reduced CAN is an off-white solid containing coordinated free ammonia. It is soluble in liquid ammonia. In air and at room temperature, the product is slowly oxidized to CeO2. At 100°C, the process takes one week. Upon addition of water, the complex appears insoluble, because of instant formation of Ce-hydroxide. A sample of reduced CAN was analysed using X-ray diffraction (Debye-camera, CuKα radiation, calibrated with Si as a standard) showing the existence of both NH4NO3 and a compound which set of reflections is presented in Table. The magnetic susceptibility Note présentée par Jean ROUXEL. 0249-6305/88/03072021 S 2.00 © Académie des Sciences 2022 C. R. Acad. Sci. Paris, t. 307, Série II, p. 2021-2026, 1988 values analysis (Fig. 1) together with the thermogravimetric analysis (TGA) with helium as the carrier gas (Fig. 2) lead to the assignment of the formula {NH4NO3-[(NH4)2Ce(III)(NO3)5,2.5NH3]}. The effective magnetic moment (2.54 + 0.03 μB) is in fair agreement with what is generally observed for Ce (III) [12], [13]. Below 150 K, the deviation from the Curie-Weiss law closely resembles to that observed for NaCeS2 for which such a behaviour has been accounted for by considering the crystal field splitting in the J = 5/2 ground state of Ce 3+ and different exchange interaction parameters [14]. As for the TGA results (Fig. 2), the compound is oxidized into CeO2 at higher temperatures as it occurs to the hydrates [15]. The material loses first the 2.5 moles of ammonia which are not strongly bound: 0.5 NH3 below 50°C, 1 NH3 below 75°C, and 1 NH3 below 110°C. The second step from 135 to 200°C corresponds to the decomposition of ammonium ions into ammonia and proton together with that of ammonium nitrate [16]. The third step, above 210°C, is the denitration of the pentanitratocerate ions. Taking into account the above results and owing to the fact that
Ce (III) [12], [13]. Below 150 K, the deviation from the Curie-Weiss law closely resembles to that observed for NaCeS2 for which such a behaviour has been accounted for by considering the crystal field splitting in the J = 5/2 ground state of Ce 3+ and different exchange interaction parameters [14]. As for the TGA results (Fig. 2), the compound is oxidized into CeO2 at higher temperatures as it occurs to the hydrates [15]. The material loses first the 2.5 moles of ammonia which are not strongly bound: 0.5 NH3 below 50°C, 1 NH3 below 75°C, and 1 NH3 below 110°C. The second step from 135 to 200°C corresponds to the decomposition of ammonium ions into ammonia and proton together with that of ammonium nitrate [16]. The third step, above 210°C, is the denitration of the pentanitratocerate ions. Taking into account the above results and owing to the fact that the oxidation of ammonia yields nitrogen and ammonium ions, the reaction of ammonia and CAN is represented by: [(NH4)2Ce(IV)(NO3)5], where Ce is ten coordinated, is thus obtained upon removal of the ammonia under vacuum and heating. This can be done also by displacing ammonia with methanol by heating under reflux. [(NH4)2Ce(NO3)5] is water soluble. Kept in the absence of humidity, it is stable indefinitely. Similarly to the use of CAN for the synthesis of Ce(IV) alkoxides and other syntheses, cerous ammonium nitrate could be used for the synthesis of the Ce(III) analogues. INTRODUCTION. — L'hexanitratocérate d'ammonium (NH4)2Ce(NO3)6, plus communément appelé nitrate de cérium ammoniacal (désigné par CAN ci-dessous), est principalement utilisé comme oxydant de groupes fonctionnels organiques. Récemment, il a été utilisé comme produit de départ dans la préparation de dérivés organiques du cérium (IV). C'est un produit plutôt stable, facile à se procurer, soluble dans de nombreux solvants tels que les alcools, le THF, le diméthoxyéthane, etc. L'ion nitrate étant un ligand bidendate, le cérium (IV) présente dans l'ion hexanitratocérate (IV) Ce(NO3)6, une coordinence très élevée, égale à 12. CAN peut être déshydraté sans décomposition par chauffage à 100-120°C, de préférence sous vide. Ce n'est généralement pas le cas
[(NH4)2Ce(NO3)5] is water soluble. Kept in the absence of humidity, it is stable indefinitely. Similarly to the use of CAN for the synthesis of Ce(IV) alkoxides and other syntheses, cerous ammonium nitrate could be used for the synthesis of the Ce(III) analogues. INTRODUCTION. — L'hexanitratocérate d'ammonium (NH4)2Ce(NO3)6, plus communément appelé nitrate de cérium ammoniacal (désigné par CAN ci-dessous), est principalement utilisé comme oxydant de groupes fonctionnels organiques. Récemment, il a été utilisé comme produit de départ dans la préparation de dérivés organiques du cérium (IV). C'est un produit plutôt stable, facile à se procurer, soluble dans de nombreux solvants tels que les alcools, le THF, le diméthoxyéthane, etc. L'ion nitrate étant un ligand bidendate, le cérium (IV) présente dans l'ion hexanitratocérate (IV) Ce(NO3)6, une coordinence très élevée, égale à 12. CAN peut être déshydraté sans décomposition par chauffage à 100-120°C, de préférence sous vide. Ce n'est généralement pas le cas des nombreux nitrates doubles de cérium (III). Un nitrate de Ce (III) tétrahydraté signalé antérieurement ferait toutefois exception. Sa déshydratation conduirait à un nitrate de cérium (III) ammoniacal (NH4)2Ce(NO3)5, dont les caractéristiques demeurent inconnues. Nous avons envisagé la préparation de ce dernier composé à partir de CAN préalablement déshydraté, par une voie facile à mettre en œuvre, en choisissant l'ammoniac comme réducteur. Dans ce cas, le seul produit secondaire susceptible de se former est l'azote. Alors que peu de données concernant l'ion pentanitratocérate (III) sont disponibles, il était intéressant d'identifier le complexe ainsi obtenu en le caractérisant par diffraction X, analyse thermique différentielle et mesure de susceptibilité magnétique. PRÉPARATION. — Le nitrate de cérium ammoniacal commercial utilisé (Rhône-Poulenc Chimie) est séché à 110°C sous vide dynamique secondaire pendant plusieurs heures et stocké dans une boîte sèche contenant moins de 10 ppm d'eau, boîte à l'intérieur de laquelle seront effectuées toutes manipulations d'échantillon. L'absence de dégradation thermique du produit de départ est vérifiée par diffractométrie X (Chambre de Debye, radiation CuKa, étalon de silicium) et par référence au spectre de poudre fourni par le National Bureau of Standards. De plus, le diamagnétisme constaté à l'aide d'une balance de Faraday de 77