The complete harmonic force field and dipole moment derivatives have been computed for toluene at... more The complete harmonic force field and dipole moment derivatives have been computed for toluene at the Hartree‐Fock level using a 4‐21G basis set. The six scale factors optimized for benzene were used to scale the computed harmonic force constants of toluene. The vibrational frequencies of toluene computed from this scaled quantum mechanical force field are quite good. After a correction was made to two previously proposed spectral assignments, the mean deviation from the experimental frequencies is only 7.8 cm−1 except for the frequencies related to the methyl group. Five more scale factors for the vibrational modes of the methyl group were reoptimized. The final comparison showed an overall mean deviation of 7.5 cm−1 between the theoretical spectrum and the experimental spectrum. Computed intensities are qualitatively in agreement with experiments. They are highly useful in the investigation of questionable assignments.
Complete scaled ab initio force fields and frequencies have been calculated for the all-trans and... more Complete scaled ab initio force fields and frequencies have been calculated for the all-trans and all-cis isomers of 1,3,5,7octatetraene. Several peaks in the infrared and Raman spectra have been reassigned, and a medium intensity IR peak at 1580 cm-' is predicted. The agreement between the experimental and theoretical CC stretching frequencies is very good. We believe that the force constants are superior to previous theoretical ones. A detailed comparison with the results from an extended Pariser-Parr-Pople configuration interaction theory is made. The effect of cis-trans isomerization is discussed. The perdeuterated frequencies are also presented in anticipation of future experimental measurements.
The direct inversion in the iterative subspace (DIIS) method is applied to several simple SCF wav... more The direct inversion in the iterative subspace (DIIS) method is applied to several simple SCF wave functions in an effective Fock matrix formulation. The following cases are treated: high-spin-restricted open shell, open-shell singlet, and two-configuration wave functions. Open-shell singlet states are described by a three-determinant 2×2 CAS expansion which is equivalent to Davidson’s nonorthogonal SCF method in the case of the first open-shell singlet. Very sharp convergence is usually obtained in less than 20 cycles. The method is applicable to slowly convergent or even inherently divergent cases, and able to enforce convergence to excited states not the lowest of their symmetry. For these simple wave functions, the present first order method is asymptotically more efficient than second-order methods. Examples are presented for H2O, H2O2, C2H4, F2, several states of NO2, C2H5, formaldehyde, and ketene.
A simple way of generating starting orbitals for multiconfigurational SCF calculations (particula... more A simple way of generating starting orbitals for multiconfigurational SCF calculations (particularly of the CAS type) is to use the natural orbitals of the unrestricted Hartree–Fock wave function. Significant fractional occupancy of a UHF natural orbital indicates that the orbital should be included in the active space; this is illustrated for symmetrically stretched water, for NO, N2O4, and for the transition state on the Me3CO→Me2CO+CH3 reaction surface. Average natural orbitals should be used if there are several UHF solutions for the same state; this restores symmetry broken at the the UHF level. Configuration selection based on fractional occupation appears to be the basis for a reliable automated procedure. The UHF natural orbitals provide good starting orbitals for the two-configuration SCF and for the 4×4 CAS wave function in stretched F2, H2O2, and C2H6, methane, water, in twisted ethylene, in ozone, and for various CAS wave functions in the first asynchronous transition state of the HCNO+H2C2 1,3-cycloaddition. Comparison is made with the extended Hartree–Fock method.
Complete scaled ab initio force fields and frequencies have been calculated for the all-trans and... more Complete scaled ab initio force fields and frequencies have been calculated for the all-trans and all-cis isomers of 1,3,5,7octatetraene. Several peaks in the infrared and Raman spectra have been reassigned, and a medium intensity IR peak at 1580 cm-' is predicted. The agreement between the experimental and theoretical CC stretching frequencies is very good. We believe that the force constants are superior to previous theoretical ones. A detailed comparison with the results from an extended Pariser-Parr-Pople configuration interaction theory is made. The effect of cis-trans isomerization is discussed. The perdeuterated frequencies are also presented in anticipation of future experimental measurements.
A simple way of generating starting orbitals for multiconfigurational SCF calculations (particula... more A simple way of generating starting orbitals for multiconfigurational SCF calculations (particularly of the CAS type) is to use the natural orbitals of the unrestricted Hartree–Fock wave function. Significant fractional occupancy of a UHF natural orbital indicates that the orbital should be included in the active space; this is illustrated for symmetrically stretched water, for NO, N2O4, and for the transition state on the Me3CO→Me2CO+CH3 reaction surface. Average natural orbitals should be used if there are several UHF solutions for the same state; this restores symmetry broken at the the UHF level. Configuration selection based on fractional occupation appears to be the basis for a reliable automated procedure. The UHF natural orbitals provide good starting orbitals for the two-configuration SCF and for the 4×4 CAS wave function in stretched F2, H2O2, and C2H6, methane, water, in twisted ethylene, in ozone, and for various CAS wave functions in the first asynchronous transition st...
Page 1. MOLECULAR PHYSICS, 1983, VOL. 50, NO. 1, 139-151 Theoretical equilibrium geometry, vibrat... more Page 1. MOLECULAR PHYSICS, 1983, VOL. 50, NO. 1, 139-151 Theoretical equilibrium geometry, vibrational frequencies and the first electronic transition energy of HCC by GI~ZA FOGARASI t and JAMES E. BOGGS Department ...
ABSTRACT The harmonic force field for the out-of-plane vibrations of pyridine has been calculated... more ABSTRACT The harmonic force field for the out-of-plane vibrations of pyridine has been calculated from ab initio Hartree-Fock wavefunctions obtained with a 4-21 basis set of contracted Gaussians. To account for systematic errors, the calculated force constants were scaled, using only two independent sclae factors which were transferred unchanged from benzene. The resulting scaled quantum mechanical force field, which is strictly a priori in that it is not based on any experimental data on pyridine, predicts the 64 out-of-plane fundamental frequencies of pyridine and its deuterated isotopomers of C2v symmetry with a mean deviation from experiment of only 8.5 cm-1. Addition of polarization functions to the basis set for the nitrogen atom and refinement of the two scale factors by fitting them to the observed pyridine spectra produce no significant improvement in the fit. Assignments of the vibrational spectra are discussed.
ABSTRACT Force constants have been calculated for H2NF and HNF2 from ab initio Hartree-Fock wavef... more ABSTRACT Force constants have been calculated for H2NF and HNF2 from ab initio Hartree-Fock wavefunctions by the force method, using 7s3p/1 gaussian basis sets. The force field of HNF2, obtained from a combination of the theoretical results with the experimental frequencies, can be considered as the most reliable one at present. Previous force fields are discussed critically. From a full optimization the predicted geometry of H2NF is: NF = 1·399 Å, NH = 1·018 Å, HNF = 102·9° and HNH = 105·9°.
Several methods of constructing the active orbital space for multiconfigurational wave functions ... more Several methods of constructing the active orbital space for multiconfigurational wave functions are compared on typical moderately strongly or strongly correlated ground-state molecules. The relative merits of these methods and problems inherent in multiconfigurational calculations are discussed. Strong correlation in the ground electronic state is found typically in larger conjugated and antiaromatic systems, transition states which involve bond breaking or formation, and transition metal complexes. Our examples include polyenes, polyacenes, the reactant, product and transition state of the Bergman cyclization, and two transition metal complexes: Hieber's anion [(CO) 3 FeNO] − and ferrocene. For the systems investigated, the simplest and oldest selection method, based on the fractional occupancy of unrestricted Hartree-Fock natural orbitals (the UNO criterion), yields the same active space as much more expensive approximate full CI methods. A disadvantage of this method used to be the difficulty of finding broken spin symmetry UHF solutions. However, our analytical method, accurate to fourth order in the orbital rotation angles (Tóth and Pulay J. Chem. Phys. 2016, 145, 164102.), has solved this problem. Two further advantages of the UNO criterion are that, unlike most other methods, it measures not only the energetic proximity to the Fermi level but also the magnitude of the exchange interaction with strongly occupied orbitals and therefore allows the estimation of the correlation strength for orbital selection in Restricted Active Space methods.
An efficient analytical energy gradient algorithm for the cluster-in-molecule (CIM) second order ... more An efficient analytical energy gradient algorithm for the cluster-in-molecule (CIM) second order Møller-Plesset perturbation theory (MP2) method is presented. In our algorithm, the gradient contributions from the nonseparable term of the two-body density matrix on a given atom is extracted from calculations on a cluster constructed for this atom. The other terms in the CIM-MP2 energy gradient expression are evaluated by constructing the density matrices of the whole system with the contributions from all clusters constructed. For basis sets with diffuse functions, tight CIM parameters are necessary to obtain accurate gradients. Benchmark calculations show that the CIM-MP2 method can accurately reproduce the conventional MP2 gradients and geometries for larger systems. The optimized structure of a 174-atom oligopeptide using the CIM-MP2 method with the cc-pVDZ basis set is in good agreement with the corresponding crystal structure. The present CIM-MP2 gradient program can be used for optimizing the geometries of large systems with hundreds of atoms on ordinary workstations.
Based on the Hylleraas functional form, the second and third orders of Møller-Plesset perturbatio... more Based on the Hylleraas functional form, the second and third orders of Møller-Plesset perturbation theory are reformulated in terms of arbitrary (e.g., localized) internal orbitals, and atomic orbitals in the virtual space. The results are strictly equivalent to the canonical formulation if no further approximations are introduced. The new formalism permits the extension of the local correlation method to Møller-Plesset
stability of the ammonium group in certain ammonium compounds. It can be postulated that even at ... more stability of the ammonium group in certain ammonium compounds. It can be postulated that even at room temperature, free protons and free electrons are being released by the ammonium group in (NH4)2S04 crystals, which then react with Mn04-to produce Mn2+. The rate of this Mn2+ production at room temperature is slow but accumulative such that it can be eventually detected by EPR. It has been shownI0 that free protons released by the ammonium group contributes to the electrical conductivity of LiNH4S04 crystals in all of its known phases, including the room-temperature and the low-temperature phases. We suggest that these free protons and free electrons participated in the room-temperature reduction of Mn04-into Mn2+ in (NH4)2S-04:Mn0, crystals. However, crystals of NH4C104:Mn04-and NH4BF4:Mn04-stored in the dark for more than 1 year did not exhibit any EPR spectrum of Mn2+. This tends to suggest that the ammonium groups in these two ammonium compounds are chemically more stable than those in (NH4)2S04. Acknowledgment. This research is supported by the National Science Council (NSC) of the Republic of China under Project Registry No. Mn04-, 14333-1 3-2; NH4C104, 7790-98-9; NH4BF4, NO. NSC8 1-0208-M003-06. 13826-83-0; Mn2+, 16397-91-4. References and Notes (1) Zimmerman, G.
A numerically accurate implementation of the gauge-including atomic orbital method for the calcul... more A numerically accurate implementation of the gauge-including atomic orbital method for the calculation of NMR shieldings in density functional theory (DFT) is presented. Results calculated by this method are compared with results of SCF and accurate coupled cluster calculations for eight small molecules. Three sets of DFT results, obtained using different exchange-correlation functionals, are further compared with each other, with the SCF data, and with experiment for a set of 10 somewhat larger organic molecules. The DFT values show a modest improvement compared to SCF theory. Potential computational savings using density functional theory are discussed.
The geometries of Dewar benzene and Dewar pyridine were fully optimized by restricted Hartree-Fwk... more The geometries of Dewar benzene and Dewar pyridine were fully optimized by restricted Hartree-Fwk theory and the 6-31G* basis set. Reference geometries for force field calculations were obtained by systematic empirical corrections. The ab initio force fields, after empirical scaling, yield frequencies which are in good agreement with experiments. On the basis of the calculations, some uncertainties in the experimental assignments of the fundamental frequencies of Dewar benzene were resolved, and assignments for the observed matrix IR frequencies of Dewar pyridine were given for the first time. This study demonstrates again the value of the scaled quantum mechanical (SQM) force field method. CH stretching CH stretching CH stretching CH stretching CH stretching C=N stretching C=C stretching CH bending CH bending CH bending CH bending CH bending CH bending CH bending CC str and CH bending CC str and CH bending CC str and CH bending CH bending and CN str skeletal def and tors CH bending and CN str CC str and CH bending CH bending and CC str skeletal def CH bending skeletal tors wing flapping skeletal tors 'Matrix IR frequencies, ref 8. *Calculated IR intensities are in km/mol. 'Relative intensities.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
The complete harmonic force field and dipole moment derivatives have been computed for toluene at... more The complete harmonic force field and dipole moment derivatives have been computed for toluene at the Hartree‐Fock level using a 4‐21G basis set. The six scale factors optimized for benzene were used to scale the computed harmonic force constants of toluene. The vibrational frequencies of toluene computed from this scaled quantum mechanical force field are quite good. After a correction was made to two previously proposed spectral assignments, the mean deviation from the experimental frequencies is only 7.8 cm−1 except for the frequencies related to the methyl group. Five more scale factors for the vibrational modes of the methyl group were reoptimized. The final comparison showed an overall mean deviation of 7.5 cm−1 between the theoretical spectrum and the experimental spectrum. Computed intensities are qualitatively in agreement with experiments. They are highly useful in the investigation of questionable assignments.
Complete scaled ab initio force fields and frequencies have been calculated for the all-trans and... more Complete scaled ab initio force fields and frequencies have been calculated for the all-trans and all-cis isomers of 1,3,5,7octatetraene. Several peaks in the infrared and Raman spectra have been reassigned, and a medium intensity IR peak at 1580 cm-' is predicted. The agreement between the experimental and theoretical CC stretching frequencies is very good. We believe that the force constants are superior to previous theoretical ones. A detailed comparison with the results from an extended Pariser-Parr-Pople configuration interaction theory is made. The effect of cis-trans isomerization is discussed. The perdeuterated frequencies are also presented in anticipation of future experimental measurements.
The direct inversion in the iterative subspace (DIIS) method is applied to several simple SCF wav... more The direct inversion in the iterative subspace (DIIS) method is applied to several simple SCF wave functions in an effective Fock matrix formulation. The following cases are treated: high-spin-restricted open shell, open-shell singlet, and two-configuration wave functions. Open-shell singlet states are described by a three-determinant 2×2 CAS expansion which is equivalent to Davidson’s nonorthogonal SCF method in the case of the first open-shell singlet. Very sharp convergence is usually obtained in less than 20 cycles. The method is applicable to slowly convergent or even inherently divergent cases, and able to enforce convergence to excited states not the lowest of their symmetry. For these simple wave functions, the present first order method is asymptotically more efficient than second-order methods. Examples are presented for H2O, H2O2, C2H4, F2, several states of NO2, C2H5, formaldehyde, and ketene.
A simple way of generating starting orbitals for multiconfigurational SCF calculations (particula... more A simple way of generating starting orbitals for multiconfigurational SCF calculations (particularly of the CAS type) is to use the natural orbitals of the unrestricted Hartree–Fock wave function. Significant fractional occupancy of a UHF natural orbital indicates that the orbital should be included in the active space; this is illustrated for symmetrically stretched water, for NO, N2O4, and for the transition state on the Me3CO→Me2CO+CH3 reaction surface. Average natural orbitals should be used if there are several UHF solutions for the same state; this restores symmetry broken at the the UHF level. Configuration selection based on fractional occupation appears to be the basis for a reliable automated procedure. The UHF natural orbitals provide good starting orbitals for the two-configuration SCF and for the 4×4 CAS wave function in stretched F2, H2O2, and C2H6, methane, water, in twisted ethylene, in ozone, and for various CAS wave functions in the first asynchronous transition state of the HCNO+H2C2 1,3-cycloaddition. Comparison is made with the extended Hartree–Fock method.
Complete scaled ab initio force fields and frequencies have been calculated for the all-trans and... more Complete scaled ab initio force fields and frequencies have been calculated for the all-trans and all-cis isomers of 1,3,5,7octatetraene. Several peaks in the infrared and Raman spectra have been reassigned, and a medium intensity IR peak at 1580 cm-' is predicted. The agreement between the experimental and theoretical CC stretching frequencies is very good. We believe that the force constants are superior to previous theoretical ones. A detailed comparison with the results from an extended Pariser-Parr-Pople configuration interaction theory is made. The effect of cis-trans isomerization is discussed. The perdeuterated frequencies are also presented in anticipation of future experimental measurements.
A simple way of generating starting orbitals for multiconfigurational SCF calculations (particula... more A simple way of generating starting orbitals for multiconfigurational SCF calculations (particularly of the CAS type) is to use the natural orbitals of the unrestricted Hartree–Fock wave function. Significant fractional occupancy of a UHF natural orbital indicates that the orbital should be included in the active space; this is illustrated for symmetrically stretched water, for NO, N2O4, and for the transition state on the Me3CO→Me2CO+CH3 reaction surface. Average natural orbitals should be used if there are several UHF solutions for the same state; this restores symmetry broken at the the UHF level. Configuration selection based on fractional occupation appears to be the basis for a reliable automated procedure. The UHF natural orbitals provide good starting orbitals for the two-configuration SCF and for the 4×4 CAS wave function in stretched F2, H2O2, and C2H6, methane, water, in twisted ethylene, in ozone, and for various CAS wave functions in the first asynchronous transition st...
Page 1. MOLECULAR PHYSICS, 1983, VOL. 50, NO. 1, 139-151 Theoretical equilibrium geometry, vibrat... more Page 1. MOLECULAR PHYSICS, 1983, VOL. 50, NO. 1, 139-151 Theoretical equilibrium geometry, vibrational frequencies and the first electronic transition energy of HCC by GI~ZA FOGARASI t and JAMES E. BOGGS Department ...
ABSTRACT The harmonic force field for the out-of-plane vibrations of pyridine has been calculated... more ABSTRACT The harmonic force field for the out-of-plane vibrations of pyridine has been calculated from ab initio Hartree-Fock wavefunctions obtained with a 4-21 basis set of contracted Gaussians. To account for systematic errors, the calculated force constants were scaled, using only two independent sclae factors which were transferred unchanged from benzene. The resulting scaled quantum mechanical force field, which is strictly a priori in that it is not based on any experimental data on pyridine, predicts the 64 out-of-plane fundamental frequencies of pyridine and its deuterated isotopomers of C2v symmetry with a mean deviation from experiment of only 8.5 cm-1. Addition of polarization functions to the basis set for the nitrogen atom and refinement of the two scale factors by fitting them to the observed pyridine spectra produce no significant improvement in the fit. Assignments of the vibrational spectra are discussed.
ABSTRACT Force constants have been calculated for H2NF and HNF2 from ab initio Hartree-Fock wavef... more ABSTRACT Force constants have been calculated for H2NF and HNF2 from ab initio Hartree-Fock wavefunctions by the force method, using 7s3p/1 gaussian basis sets. The force field of HNF2, obtained from a combination of the theoretical results with the experimental frequencies, can be considered as the most reliable one at present. Previous force fields are discussed critically. From a full optimization the predicted geometry of H2NF is: NF = 1·399 Å, NH = 1·018 Å, HNF = 102·9° and HNH = 105·9°.
Several methods of constructing the active orbital space for multiconfigurational wave functions ... more Several methods of constructing the active orbital space for multiconfigurational wave functions are compared on typical moderately strongly or strongly correlated ground-state molecules. The relative merits of these methods and problems inherent in multiconfigurational calculations are discussed. Strong correlation in the ground electronic state is found typically in larger conjugated and antiaromatic systems, transition states which involve bond breaking or formation, and transition metal complexes. Our examples include polyenes, polyacenes, the reactant, product and transition state of the Bergman cyclization, and two transition metal complexes: Hieber's anion [(CO) 3 FeNO] − and ferrocene. For the systems investigated, the simplest and oldest selection method, based on the fractional occupancy of unrestricted Hartree-Fock natural orbitals (the UNO criterion), yields the same active space as much more expensive approximate full CI methods. A disadvantage of this method used to be the difficulty of finding broken spin symmetry UHF solutions. However, our analytical method, accurate to fourth order in the orbital rotation angles (Tóth and Pulay J. Chem. Phys. 2016, 145, 164102.), has solved this problem. Two further advantages of the UNO criterion are that, unlike most other methods, it measures not only the energetic proximity to the Fermi level but also the magnitude of the exchange interaction with strongly occupied orbitals and therefore allows the estimation of the correlation strength for orbital selection in Restricted Active Space methods.
An efficient analytical energy gradient algorithm for the cluster-in-molecule (CIM) second order ... more An efficient analytical energy gradient algorithm for the cluster-in-molecule (CIM) second order Møller-Plesset perturbation theory (MP2) method is presented. In our algorithm, the gradient contributions from the nonseparable term of the two-body density matrix on a given atom is extracted from calculations on a cluster constructed for this atom. The other terms in the CIM-MP2 energy gradient expression are evaluated by constructing the density matrices of the whole system with the contributions from all clusters constructed. For basis sets with diffuse functions, tight CIM parameters are necessary to obtain accurate gradients. Benchmark calculations show that the CIM-MP2 method can accurately reproduce the conventional MP2 gradients and geometries for larger systems. The optimized structure of a 174-atom oligopeptide using the CIM-MP2 method with the cc-pVDZ basis set is in good agreement with the corresponding crystal structure. The present CIM-MP2 gradient program can be used for optimizing the geometries of large systems with hundreds of atoms on ordinary workstations.
Based on the Hylleraas functional form, the second and third orders of Møller-Plesset perturbatio... more Based on the Hylleraas functional form, the second and third orders of Møller-Plesset perturbation theory are reformulated in terms of arbitrary (e.g., localized) internal orbitals, and atomic orbitals in the virtual space. The results are strictly equivalent to the canonical formulation if no further approximations are introduced. The new formalism permits the extension of the local correlation method to Møller-Plesset
stability of the ammonium group in certain ammonium compounds. It can be postulated that even at ... more stability of the ammonium group in certain ammonium compounds. It can be postulated that even at room temperature, free protons and free electrons are being released by the ammonium group in (NH4)2S04 crystals, which then react with Mn04-to produce Mn2+. The rate of this Mn2+ production at room temperature is slow but accumulative such that it can be eventually detected by EPR. It has been shownI0 that free protons released by the ammonium group contributes to the electrical conductivity of LiNH4S04 crystals in all of its known phases, including the room-temperature and the low-temperature phases. We suggest that these free protons and free electrons participated in the room-temperature reduction of Mn04-into Mn2+ in (NH4)2S-04:Mn0, crystals. However, crystals of NH4C104:Mn04-and NH4BF4:Mn04-stored in the dark for more than 1 year did not exhibit any EPR spectrum of Mn2+. This tends to suggest that the ammonium groups in these two ammonium compounds are chemically more stable than those in (NH4)2S04. Acknowledgment. This research is supported by the National Science Council (NSC) of the Republic of China under Project Registry No. Mn04-, 14333-1 3-2; NH4C104, 7790-98-9; NH4BF4, NO. NSC8 1-0208-M003-06. 13826-83-0; Mn2+, 16397-91-4. References and Notes (1) Zimmerman, G.
A numerically accurate implementation of the gauge-including atomic orbital method for the calcul... more A numerically accurate implementation of the gauge-including atomic orbital method for the calculation of NMR shieldings in density functional theory (DFT) is presented. Results calculated by this method are compared with results of SCF and accurate coupled cluster calculations for eight small molecules. Three sets of DFT results, obtained using different exchange-correlation functionals, are further compared with each other, with the SCF data, and with experiment for a set of 10 somewhat larger organic molecules. The DFT values show a modest improvement compared to SCF theory. Potential computational savings using density functional theory are discussed.
The geometries of Dewar benzene and Dewar pyridine were fully optimized by restricted Hartree-Fwk... more The geometries of Dewar benzene and Dewar pyridine were fully optimized by restricted Hartree-Fwk theory and the 6-31G* basis set. Reference geometries for force field calculations were obtained by systematic empirical corrections. The ab initio force fields, after empirical scaling, yield frequencies which are in good agreement with experiments. On the basis of the calculations, some uncertainties in the experimental assignments of the fundamental frequencies of Dewar benzene were resolved, and assignments for the observed matrix IR frequencies of Dewar pyridine were given for the first time. This study demonstrates again the value of the scaled quantum mechanical (SQM) force field method. CH stretching CH stretching CH stretching CH stretching CH stretching C=N stretching C=C stretching CH bending CH bending CH bending CH bending CH bending CH bending CH bending CC str and CH bending CC str and CH bending CC str and CH bending CH bending and CN str skeletal def and tors CH bending and CN str CC str and CH bending CH bending and CC str skeletal def CH bending skeletal tors wing flapping skeletal tors 'Matrix IR frequencies, ref 8. *Calculated IR intensities are in km/mol. 'Relative intensities.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
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