Marian Lowe - Academia.edu (original) (raw)
Papers by Marian Lowe
Author Institution: Department of Chemistry, University of Southern California; Department of The... more Author Institution: Department of Chemistry, University of Southern California; Department of Theoretical Chemistry, Cambridge University; Department of Chemistry, Boston University
The Journal of Physical Chemistry, Nov 1, 1988
Vibrational circular dichroism spectra of (R)-methylthiirane are calculated by using Stephens' eq... more Vibrational circular dichroism spectra of (R)-methylthiirane are calculated by using Stephens' equations for the vibrational-rotational strengths in the distributed origin gauge, the common origin gauge with the origin at the center of mass of the molecule, and the common origin gauge with the origin at the sulfur atom. The scaled quantum mechanical force field at a corrected theoretical geometry is used to calculate the atomic displacement matrix. All calculations are performed using the 6-31G* basis set. The three calculated spectra are compared with the experimental one. Best agreement is found with the origin at the center of mass.
Chemischer Informationsdienst, May 13, 1986
Spectrochimica acta, 1988
ABSTRACT
The Journal of Physical Chemistry, 1988
Vibrational circular dichroism spectra of (R)-methylthiirane are calculated by using Stephens' eq... more Vibrational circular dichroism spectra of (R)-methylthiirane are calculated by using Stephens' equations for the vibrational-rotational strengths in the distributed origin gauge, the common origin gauge with the origin at the center of mass of the molecule, and the common origin gauge with the origin at the sulfur atom. The scaled quantum mechanical force field at a corrected theoretical geometry is used to calculate the atomic displacement matrix. All calculations are performed using the 6-31G* basis set. The three calculated spectra are compared with the experimental one. Best agreement is found with the origin at the center of mass.
Journal of the Chemical Society, Chemical Communications, 1973
An i.r. absorption band found at 535 cm–1 corresponds to an absorption in the photoexcited triple... more An i.r. absorption band found at 535 cm–1 corresponds to an absorption in the photoexcited triplet state of the [2H8]naphthalene molecule.
Physical Review Letters, 1968
Physical Review, Jul 10, 1968
The 6ne structure of the zero-phonon 'T2, state of AI203. . V'+ arising from the trigonal field a... more The 6ne structure of the zero-phonon 'T2, state of AI203. . V'+ arising from the trigonal field and spin-orbit coupling is anomalously small. Ligand-field theory predicts a 400-cm splitting, while the observed levels, first fully identified by Scott and Sturge, span only 14 cm ', This has been attributed to a large tetragonal Jahn-Teller e8ect, and a detailed analysis of the zero-phonon levels was made by Scott and Sturge on the basis of Ham's model calculations for octahedral molecules. We have made new measurements on the 0-0 T2, band, including the axial spectrum, which shows one 0-polarized transition to be magnetic dipole in origin, and the Zeeman effect of the~and 0 spectra at 10'K in fields up to 40 kG parallel and perpendicular to the trigonal axis. The validity of the Ham-Scott-Sturge model has also been further investigated. We have shown that the details of the Scott-Sturge theory require modification, and that it is possible to explain the observed zero-6eld level pattern within the framework of Ham's general model if, but only if, the assumption of equal quenching of first-order trigonal field and spin-orbit splittings is dropped. In addition, we have obtained values of the firstand second-order trigonal field and spin-orbit coupling energies which reproduce quantitatively the zero-6eld energies, Zeeman behavior, selection rules, and intensities of all transitions. It is found that the first-order spin-orbit splitting is some four times less quenched than the 6rst-order trigonal-field splitting.
Chemischer Informationsdienst, May 20, 1986
1^{1}1 I.W. Levin and R.A.R. Pearce, J. Chem. Phys. 69, 2195 (1978). 2^{2}2 C.E. Blom and C. Alto... more $^{1}$ I.W. Levin and R.A.R. Pearce, J. Chem. Phys. 69, 2195 (1978). 2^{2}2 C.E. Blom and C. Altona, Molec. Phys. 31, 1377 (1976). ast^{\ast}ast Permanent address of Lowe: Department of Chemistry, Boston University, Boston, Mass. 02215.ss
Chemical Physics, Apr 1, 1988
The scaled quantum mechanical (SQM) method for calculating the vibrational structure of molecules... more The scaled quantum mechanical (SQM) method for calculating the vibrational structure of molecules is applied to the solvated glycine zwitterion. The ab initio force field generated by means of a molecular dynamics calculation [J.S. Alper, H. Dothe and D.F. Coker, Chem. Phys. I53 (1991) 5 1 ] was scaled using the frequencies from experimental spectra taken in aqueous solution. Theoretical frequencies, potential energy distributions, intensities, and line shapes were obtained. The theoretical frequencies and normal mode assignments were in excellent agreement with the aqueous spectra. Theoretical frequencies and normal modes calculated by scaling to frequencies obtained from the experimental a-crystal spectra of glycine were in significantly worse agreement with the experimental crystalline values. These results suggest that the calculation has distinguished the aqueous from the crystalline environment.
The Journal of Physical Chemistry, 1986
Author Institution: Department of Chemistry, University of Southern CaliforniaThe vibrational abs... more Author Institution: Department of Chemistry, University of Southern CaliforniaThe vibrational absorption and CD spectrum of propylene oxide are presented and analysed. Experimental spectra have been obtained in solution at room temperature and in N2N_{2}N2 matrices at sim20circK\sim 20^{\circ}Ksim20circK. Calculations of the VCD spectrum using various force fields and theoretical methodologies, including the new ab initio formalism, are reported and discussed. Comparison of our results with those of Polavorapu and Michalska is made
Physical Review, 1968
The 6ne structure of the zero-phonon 'T2, state of AI203. . V'+ arising from the trigonal field a... more The 6ne structure of the zero-phonon 'T2, state of AI203. . V'+ arising from the trigonal field and spin-orbit coupling is anomalously small. Ligand-field theory predicts a 400-cm splitting, while the observed levels, first fully identified by Scott and Sturge, span only 14 cm ', This has been attributed to a large tetragonal Jahn-Teller e8ect, and a detailed analysis of the zero-phonon levels was made by Scott and Sturge on the basis of Ham's model calculations for octahedral molecules. We have made new measurements on the 0-0 T2, band, including the axial spectrum, which shows one 0-polarized transition to be magnetic dipole in origin, and the Zeeman effect of the~and 0 spectra at 10'K in fields up to 40 kG parallel and perpendicular to the trigonal axis. The validity of the Ham-Scott-Sturge model has also been further investigated. We have shown that the details of the Scott-Sturge theory require modification, and that it is possible to explain the observed zero-6eld level pattern within the framework of Ham's general model if, but only if, the assumption of equal quenching of first-order trigonal field and spin-orbit splittings is dropped. In addition, we have obtained values of the firstand second-order trigonal field and spin-orbit coupling energies which reproduce quantitatively the zero-6eld energies, Zeeman behavior, selection rules, and intensities of all transitions. It is found that the first-order spin-orbit splitting is some four times less quenched than the 6rst-order trigonal-field splitting.
The Journal of Physical Chemistry, 1988
A theory that allows the rigorous calculation of vibrational rotational strengths was recently de... more A theory that allows the rigorous calculation of vibrational rotational strengths was recently developed by Stephens. We describe here implementation of the theory for the molecule propylene oxide using ab initio wave functions calculated with a moderate size basis set. We explore sensitivity of the calculated vibrational rotational strengths to change in geometry and to change in the force field.
Physical Review, 1969
As noted by Bloch, ' two roots are found for n'(T), which is equal to Iuw in the present paper, i... more As noted by Bloch, ' two roots are found for n'(T), which is equal to Iuw in the present paper, in the range of temperature O'K-T~'. One of these roots, which is denoted by the solid line, corresponds in the low-temperature limit to the standard results of the spin-wave theory, and the other, which is denoted by the dashed line, corresponds to a dubious solution. As can be seen in Fig. 2, 1-Ie corresponding to the standard solution is positive in the temperature range O'K-T0 and it is negative for To&T&T~'. On the other hand, 1uv corresponding to the dubious P H YS ICAL REVIEW VOLUME i80, NUMBER 2 io APRIL i969
Author Institution: Department of Chemistry, University of Southern California; Department of The... more Author Institution: Department of Chemistry, University of Southern California; Department of Theoretical Chemistry, Cambridge University; Department of Chemistry, Boston University
The Journal of Physical Chemistry, Nov 1, 1988
Vibrational circular dichroism spectra of (R)-methylthiirane are calculated by using Stephens' eq... more Vibrational circular dichroism spectra of (R)-methylthiirane are calculated by using Stephens' equations for the vibrational-rotational strengths in the distributed origin gauge, the common origin gauge with the origin at the center of mass of the molecule, and the common origin gauge with the origin at the sulfur atom. The scaled quantum mechanical force field at a corrected theoretical geometry is used to calculate the atomic displacement matrix. All calculations are performed using the 6-31G* basis set. The three calculated spectra are compared with the experimental one. Best agreement is found with the origin at the center of mass.
Chemischer Informationsdienst, May 13, 1986
Spectrochimica acta, 1988
ABSTRACT
The Journal of Physical Chemistry, 1988
Vibrational circular dichroism spectra of (R)-methylthiirane are calculated by using Stephens' eq... more Vibrational circular dichroism spectra of (R)-methylthiirane are calculated by using Stephens' equations for the vibrational-rotational strengths in the distributed origin gauge, the common origin gauge with the origin at the center of mass of the molecule, and the common origin gauge with the origin at the sulfur atom. The scaled quantum mechanical force field at a corrected theoretical geometry is used to calculate the atomic displacement matrix. All calculations are performed using the 6-31G* basis set. The three calculated spectra are compared with the experimental one. Best agreement is found with the origin at the center of mass.
Journal of the Chemical Society, Chemical Communications, 1973
An i.r. absorption band found at 535 cm–1 corresponds to an absorption in the photoexcited triple... more An i.r. absorption band found at 535 cm–1 corresponds to an absorption in the photoexcited triplet state of the [2H8]naphthalene molecule.
Physical Review Letters, 1968
Physical Review, Jul 10, 1968
The 6ne structure of the zero-phonon 'T2, state of AI203. . V'+ arising from the trigonal field a... more The 6ne structure of the zero-phonon 'T2, state of AI203. . V'+ arising from the trigonal field and spin-orbit coupling is anomalously small. Ligand-field theory predicts a 400-cm splitting, while the observed levels, first fully identified by Scott and Sturge, span only 14 cm ', This has been attributed to a large tetragonal Jahn-Teller e8ect, and a detailed analysis of the zero-phonon levels was made by Scott and Sturge on the basis of Ham's model calculations for octahedral molecules. We have made new measurements on the 0-0 T2, band, including the axial spectrum, which shows one 0-polarized transition to be magnetic dipole in origin, and the Zeeman effect of the~and 0 spectra at 10'K in fields up to 40 kG parallel and perpendicular to the trigonal axis. The validity of the Ham-Scott-Sturge model has also been further investigated. We have shown that the details of the Scott-Sturge theory require modification, and that it is possible to explain the observed zero-6eld level pattern within the framework of Ham's general model if, but only if, the assumption of equal quenching of first-order trigonal field and spin-orbit splittings is dropped. In addition, we have obtained values of the firstand second-order trigonal field and spin-orbit coupling energies which reproduce quantitatively the zero-6eld energies, Zeeman behavior, selection rules, and intensities of all transitions. It is found that the first-order spin-orbit splitting is some four times less quenched than the 6rst-order trigonal-field splitting.
Chemischer Informationsdienst, May 20, 1986
1^{1}1 I.W. Levin and R.A.R. Pearce, J. Chem. Phys. 69, 2195 (1978). 2^{2}2 C.E. Blom and C. Alto... more $^{1}$ I.W. Levin and R.A.R. Pearce, J. Chem. Phys. 69, 2195 (1978). 2^{2}2 C.E. Blom and C. Altona, Molec. Phys. 31, 1377 (1976). ast^{\ast}ast Permanent address of Lowe: Department of Chemistry, Boston University, Boston, Mass. 02215.ss
Chemical Physics, Apr 1, 1988
The scaled quantum mechanical (SQM) method for calculating the vibrational structure of molecules... more The scaled quantum mechanical (SQM) method for calculating the vibrational structure of molecules is applied to the solvated glycine zwitterion. The ab initio force field generated by means of a molecular dynamics calculation [J.S. Alper, H. Dothe and D.F. Coker, Chem. Phys. I53 (1991) 5 1 ] was scaled using the frequencies from experimental spectra taken in aqueous solution. Theoretical frequencies, potential energy distributions, intensities, and line shapes were obtained. The theoretical frequencies and normal mode assignments were in excellent agreement with the aqueous spectra. Theoretical frequencies and normal modes calculated by scaling to frequencies obtained from the experimental a-crystal spectra of glycine were in significantly worse agreement with the experimental crystalline values. These results suggest that the calculation has distinguished the aqueous from the crystalline environment.
The Journal of Physical Chemistry, 1986
Author Institution: Department of Chemistry, University of Southern CaliforniaThe vibrational abs... more Author Institution: Department of Chemistry, University of Southern CaliforniaThe vibrational absorption and CD spectrum of propylene oxide are presented and analysed. Experimental spectra have been obtained in solution at room temperature and in N2N_{2}N2 matrices at sim20circK\sim 20^{\circ}Ksim20circK. Calculations of the VCD spectrum using various force fields and theoretical methodologies, including the new ab initio formalism, are reported and discussed. Comparison of our results with those of Polavorapu and Michalska is made
Physical Review, 1968
The 6ne structure of the zero-phonon 'T2, state of AI203. . V'+ arising from the trigonal field a... more The 6ne structure of the zero-phonon 'T2, state of AI203. . V'+ arising from the trigonal field and spin-orbit coupling is anomalously small. Ligand-field theory predicts a 400-cm splitting, while the observed levels, first fully identified by Scott and Sturge, span only 14 cm ', This has been attributed to a large tetragonal Jahn-Teller e8ect, and a detailed analysis of the zero-phonon levels was made by Scott and Sturge on the basis of Ham's model calculations for octahedral molecules. We have made new measurements on the 0-0 T2, band, including the axial spectrum, which shows one 0-polarized transition to be magnetic dipole in origin, and the Zeeman effect of the~and 0 spectra at 10'K in fields up to 40 kG parallel and perpendicular to the trigonal axis. The validity of the Ham-Scott-Sturge model has also been further investigated. We have shown that the details of the Scott-Sturge theory require modification, and that it is possible to explain the observed zero-6eld level pattern within the framework of Ham's general model if, but only if, the assumption of equal quenching of first-order trigonal field and spin-orbit splittings is dropped. In addition, we have obtained values of the firstand second-order trigonal field and spin-orbit coupling energies which reproduce quantitatively the zero-6eld energies, Zeeman behavior, selection rules, and intensities of all transitions. It is found that the first-order spin-orbit splitting is some four times less quenched than the 6rst-order trigonal-field splitting.
The Journal of Physical Chemistry, 1988
A theory that allows the rigorous calculation of vibrational rotational strengths was recently de... more A theory that allows the rigorous calculation of vibrational rotational strengths was recently developed by Stephens. We describe here implementation of the theory for the molecule propylene oxide using ab initio wave functions calculated with a moderate size basis set. We explore sensitivity of the calculated vibrational rotational strengths to change in geometry and to change in the force field.
Physical Review, 1969
As noted by Bloch, ' two roots are found for n'(T), which is equal to Iuw in the present paper, i... more As noted by Bloch, ' two roots are found for n'(T), which is equal to Iuw in the present paper, in the range of temperature O'K-T~'. One of these roots, which is denoted by the solid line, corresponds in the low-temperature limit to the standard results of the spin-wave theory, and the other, which is denoted by the dashed line, corresponds to a dubious solution. As can be seen in Fig. 2, 1-Ie corresponding to the standard solution is positive in the temperature range O'K-T0 and it is negative for To&T&T~'. On the other hand, 1uv corresponding to the dubious P H YS ICAL REVIEW VOLUME i80, NUMBER 2 io APRIL i969