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Nuclear magnetic resonance-paramagnetic relaxation enhancements: Influence of spatial quantization of the electron spin when the zero-field splitting energy is larger than the Zeeman energy (1998)

Abernathy, S. M. ; Miller, J. C. ; Lohr, L. L. ; [et al.]

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 109 (1998), S. 4035-4046

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ISSN: 1089-7690

Source: AIP Digital Archive

Topics: Physics , Chemistry and Pharmacology

Notes: Dissolved paramagnetic ions generally provide an efficient mechanism for the relaxation of nuclear spins in solution, a phenomenon called the nuclear magnetic resonance-paramagnetic relaxation enhancement (NMR-PRE). Metal ions with electron spins S≥1 exhibit rich NMR relaxation phenomena originating in the properties of the zero-field splitting (zfs) interaction, which vanishes for spin-〈fraction SHAPE="CASE"〉12 ions but which is nonzero for S≥1 ions in site symmetry lower than cubic. For S≥1 ions in the vicinity of the zfs-limit, i.e., at magnetic-field strengths low enough that the zfs energy exceeds the Zeeman energy, the NMR-PRE depends strongly on the detailed structure of the electron spin energy levels as well as on the spatial quantization of the spin motion. It is shown theoretically and experimentally that the NMR-PRE produced by integer spins can be influenced strongly by the small intradoublet zero-field splittings, i.e., the splittings between the components of the non-Kramers doublets, which are produced by noncylindrical components of the crystal field potential. These small splittings produce relatively low-frequency oscillations in the dipolar field associated with 〈Sz(circumflex)〉 (the spin component along the molecule-fixed z(circumflex) axis). These motions decouple the nuclear spin from the electron spin, thereby depressing, in some cases very strongly, the NMR-PRE. The presence of a relatively small Zeeman field, comparable in magnitude to the intradoublet spacing but small compared to the larger interdoublet zfs splittings, causes a major change in the spin wave functions which has profound effects on the motions of the electron spin. When the Zeeman energy exceeds the small zfs splitting, the oscillatory motion of 〈Sz(circumflex)〉 damps out, with the result that the electron spin couples more effectively to the nuclear spin, providing a more efficient NMR relaxation pathway. NMR-PRE data are presented for the S=1 complex Ni(II)(o-pda)2Cl2 (o-pda=ortho-phenylenediamine) which confirm the importance of the splitting of the mS=±1 non-Kramers doublet on the NMR relaxation efficiency. The zfs E-parameter was measured from the NMR data to be |E|=0.26 cm−1. The S=2 spin system, Mn(III)-tetraphenylporphyrin sulfonate, exhibits a related phenomenon which arises from the effects of a small zfs splitting, Δε±2, of the mS=±2 non-Kramers doublet that is caused by a fourfold rotational component of the crystal field potential. The splitting Δε±2 was measured from NMR data to be 0.20 cm−1. © 1998 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.477003

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Assessment of temperature-dependent development in the general population and among isofemale lines ofCoccinella trifasciata (Col.: Coccinellidae) (1995)

Miller, J. C. ; LaMana, M. L.

Springer

BioControl 40 (1995), S. 183-192

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ISSN: 1573-8248

Keywords: Coccinella trifasciata ; Coccinellidae ; developmental threshold ; degree-days ; isofemale lines

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Description / Table of Contents: Résumé L'effet de la température sur le développement deCoccinella trifasciata (provenant de Corvallis, Oregon) a été étudié pour la population générale et comparé entre lignées isofemelles. Aucum œuf ne survit à 10 et 34°C. Le taux de survie est compris entre 63,3% et 96,7% pour des températures situées entre 18 et 34°C. La durée du développement, de la ponte à l'état adulte, dure de 44,2 jours à 18°C à 11,1 jours pour une température de 34°C. Le poids moyen de l'adulte ne change pas en fonction de la température et il est de 15,2 mg. Pour l'espèce, les besoins pour le développement complet de l'œuf à l'adulte, sont de 227 degrés-jour au-dessus du seuil de développement de 12,7°C. Les valeurs de ce seuil diffèrent entre les lignées isofemelles et sont comprises entre 11,4 et 14,5°C pour des durées se situant entre 186 et 260 degrés-jour au-dessus des seuils respectifs. La lignée isofemelle ayant la vitesse de développement larvaire la plus rapide à 18°C est caractérisée par un besoin de 260 degrés-jour au-dessus du seuil de 11,4°C. Celle ayant la vitesse de développement la plus lente à 18°C est caractérisée par un besoin de 186 degrés-jour au-dessus du seuil de 14,5°C. L'intérêt de l'utilisation de lignées isofemelles dans l'élevage d'agents de lutte biologique est discuté.

Notes: Abstract Temperature-dependent development ofCoccinella trifasciata LeConte from Corvallis, Oregon, was assessed for the general population and compared among a subset of isofemale lines. All eggs died at 10 and 34°C. Survival ranged between 63.3–96.7% from 18–34°C. Development from oviposition to adult ranged from 44.2 days at 18°C to 11.1 days at 34°C. Mean adult weight did not differ among temperatures, and was 15.2 mg overall. For the species, heat-unit requirements for development from egg to adult were 227 degree-days above a developmental threshold of 12.7°C. Values for the developmental threshold differed among isofemale lines, and ranged from 11.4–14.5°C with heat-unit requirements ranging from 186–260 degree-days above their respective threshold. The isofemale line producing the fastest rate of immature development at 18°C was characterized by a heat-unit requirement of 260 degree-days above a developmental threshold of 11.4°C. The isofemale line producing the slowest rate of immature development at 18°C was characterized by a heat-unit requirement of 186 degree-days above a developmental threshold of 14.5°C. Implications of using isofemale lines in culturing biological control agents are discussed.