Zeeman Effect in Porphyrins

Zero-Field Splitting of the Excited Electronic States

John C. Sutherland, Daniel Axelrod, M. P. Klein

Research output: Contribution to journalArticle

34 Citations (Scopus)

Abstract

Recent experimental studies have reported anomalous and contradictory results for the absorption of left and right circularly polarized light (LCPL and RCPL) by zinc and magnesium coproporphyrins in the presence of a magnetic field: for both compounds, the absorption bands for right and left circularly polarized light have distinctly different shapes at room temperature; at 77°K unexplained shoulders appear in the absorption spectra for both polarizations for the magnesium but not for the zinc compound; the value of the angular momentum of the lowest energy excited state computed from the separation of the peaks of the LCPL and RCPL absorption bands differs from the value obtained from magnetic circular dichroism (MCD) experiments by nearly 50%; no shape anomalies were observed in the MCD spectra. We derive a general solution for the mixing of two states by a magnetic field and show that all of the anomalous experimental data are explained if (a) the presumably degenerate pair of excited states are split in zero field by an energy comparable to the Zeeman energy but less than the spectral bandwidths, and also (b) the overlapping transitions have unequal intensities. Our results show that MCD should give better estimates of excited state angular momenta while the direct measurement of LCPL and RCPL is superior in detecting nondegeneracy.

Original languageEnglish (US)
Pages (from-to)2888-2898
Number of pages11
JournalThe Journal of Chemical Physics
Volume54
Issue number7
DOIs
StatePublished - Jan 1 1971
Externally publishedYes

Fingerprint

Zeeman effect
Porphyrins
Electronic states
Excited states
porphyrins
dichroism
Absorption spectra
Angular momentum
Light polarization
absorption spectra
Magnesium
polarized light
magnesium
Zinc Compounds
angular momentum
electronics
Coproporphyrins
zinc compounds
Magnetic fields
excitation

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

Cite this

Zeeman Effect in Porphyrins : Zero-Field Splitting of the Excited Electronic States. / Sutherland, John C.; Axelrod, Daniel; Klein, M. P.

In: The Journal of Chemical Physics, Vol. 54, No. 7, 01.01.1971, p. 2888-2898.

Research output: Contribution to journalArticle

@article{8446f5293bd746bb9f6c8e0afaff9ce0,
title = "Zeeman Effect in Porphyrins: Zero-Field Splitting of the Excited Electronic States",
abstract = "Recent experimental studies have reported anomalous and contradictory results for the absorption of left and right circularly polarized light (LCPL and RCPL) by zinc and magnesium coproporphyrins in the presence of a magnetic field: for both compounds, the absorption bands for right and left circularly polarized light have distinctly different shapes at room temperature; at 77°K unexplained shoulders appear in the absorption spectra for both polarizations for the magnesium but not for the zinc compound; the value of the angular momentum of the lowest energy excited state computed from the separation of the peaks of the LCPL and RCPL absorption bands differs from the value obtained from magnetic circular dichroism (MCD) experiments by nearly 50{\%}; no shape anomalies were observed in the MCD spectra. We derive a general solution for the mixing of two states by a magnetic field and show that all of the anomalous experimental data are explained if (a) the presumably degenerate pair of excited states are split in zero field by an energy comparable to the Zeeman energy but less than the spectral bandwidths, and also (b) the overlapping transitions have unequal intensities. Our results show that MCD should give better estimates of excited state angular momenta while the direct measurement of LCPL and RCPL is superior in detecting nondegeneracy.",
author = "Sutherland, {John C.} and Daniel Axelrod and Klein, {M. P.}",
year = "1971",
month = "1",
day = "1",
doi = "10.1063/1.1675269",
language = "English (US)",
volume = "54",
pages = "2888--2898",
journal = "Journal of Chemical Physics",
issn = "0021-9606",
publisher = "American Institute of Physics Publising LLC",
number = "7",

}

TY - JOUR

T1 - Zeeman Effect in Porphyrins

T2 - Zero-Field Splitting of the Excited Electronic States

AU - Sutherland, John C.

AU - Axelrod, Daniel

AU - Klein, M. P.

PY - 1971/1/1

Y1 - 1971/1/1

N2 - Recent experimental studies have reported anomalous and contradictory results for the absorption of left and right circularly polarized light (LCPL and RCPL) by zinc and magnesium coproporphyrins in the presence of a magnetic field: for both compounds, the absorption bands for right and left circularly polarized light have distinctly different shapes at room temperature; at 77°K unexplained shoulders appear in the absorption spectra for both polarizations for the magnesium but not for the zinc compound; the value of the angular momentum of the lowest energy excited state computed from the separation of the peaks of the LCPL and RCPL absorption bands differs from the value obtained from magnetic circular dichroism (MCD) experiments by nearly 50%; no shape anomalies were observed in the MCD spectra. We derive a general solution for the mixing of two states by a magnetic field and show that all of the anomalous experimental data are explained if (a) the presumably degenerate pair of excited states are split in zero field by an energy comparable to the Zeeman energy but less than the spectral bandwidths, and also (b) the overlapping transitions have unequal intensities. Our results show that MCD should give better estimates of excited state angular momenta while the direct measurement of LCPL and RCPL is superior in detecting nondegeneracy.

AB - Recent experimental studies have reported anomalous and contradictory results for the absorption of left and right circularly polarized light (LCPL and RCPL) by zinc and magnesium coproporphyrins in the presence of a magnetic field: for both compounds, the absorption bands for right and left circularly polarized light have distinctly different shapes at room temperature; at 77°K unexplained shoulders appear in the absorption spectra for both polarizations for the magnesium but not for the zinc compound; the value of the angular momentum of the lowest energy excited state computed from the separation of the peaks of the LCPL and RCPL absorption bands differs from the value obtained from magnetic circular dichroism (MCD) experiments by nearly 50%; no shape anomalies were observed in the MCD spectra. We derive a general solution for the mixing of two states by a magnetic field and show that all of the anomalous experimental data are explained if (a) the presumably degenerate pair of excited states are split in zero field by an energy comparable to the Zeeman energy but less than the spectral bandwidths, and also (b) the overlapping transitions have unequal intensities. Our results show that MCD should give better estimates of excited state angular momenta while the direct measurement of LCPL and RCPL is superior in detecting nondegeneracy.

UR - http://www.scopus.com/inward/record.url?scp=36849099150&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=36849099150&partnerID=8YFLogxK

U2 - 10.1063/1.1675269

DO - 10.1063/1.1675269

M3 - Article

VL - 54

SP - 2888

EP - 2898

JO - Journal of Chemical Physics

JF - Journal of Chemical Physics

SN - 0021-9606

IS - 7

ER -