Light Scattering in Electric Fields

Jennings, B. R.

doi:10.1007/978-1-4684-3914-4_9

Cited by 4 publications

(6 citation statements)

References 43 publications

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“…72,73 The dependence of scattered intensity on the scattering direction is represented by the scattering form factor P͑q͒, with q being the scattering vector with modulus q = ͑4 / ͒ − sin͑ s /2͒, where is the radiation wavelength and s is the angle subtended by the scattering direction and the prolongation of the incident beam. When the macromolecule is deformed in an electric field, it may be possible to obtain some components of the gyration tensor from scattering with various geometries.…”

Section: G Relaxation Of the Deformation Produced By The Fieldmentioning

confidence: 99%

Transient electric birefringence of wormlike macromolecules in electric fields of arbitrary strength: A computer simulation study

Pérez‐Sánchez¹,

Torre²,

Baños³

2005

The Journal of Chemical Physics

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We have studied the birefringence decay of linear models of macromolecules for two different types of flexibility, the broken-rod chain and the wormlike chain, using a computer simulation of a transient electric birefringence experiment. We have paid particular attention to the influence of the intensity of the orienting field, including two orienting mechanisms, the induced dipole, and the permanent dipole. We have compared wormlike and broken-rod models of the same radius of gyration, finding that they present a different decay curve under the influence of the same intensity of the field. We have seen that these differences are due to the faster relaxation times (smaller in the wormlike chain model) and amplitudes, because, regardless of the type of flexibility, the overall size of a molecule (measured by the radius of gyration) essentially determines the longest relaxation time. We have also analyzed how the relaxation process is affected by the degree of flexibility, the orientation mechanisms, and the intensity of the field. Studying a different aspect, we have paid attention to the deformation of a molecule in a transient electric birefringence experiment as a source of information. In this work we have developed equations to characterize this deformation in terms of one of the components of the gyration tensor, if a dynamic light scattering experiment under the influence of an electric field could be performed. To develop this work we have simulated the Brownian dynamics of the different models, relaxing after the removal of an orienting external electric field of arbitrary strength. A comparison with other methods such a the rigid body treatment or the correlation analysis of Brownian trajectories has also been included. We have seen that differences between the two Brownian dynamics methods are small and that the rigid-body treatment is only an acceptable approximation to obtain the longest relaxation time.

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Section: G Relaxation Of the Deformation Produced By The Fieldmentioning

confidence: 99%

Transient electric birefringence of wormlike macromolecules in electric fields of arbitrary strength: A computer simulation study

Pérez‐Sánchez¹,

Torre²,

Baños³

2005

The Journal of Chemical Physics

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“…Instrumental and theoretical aspects of the technique of electric field light scattering have been described in the literature. 26,27 The dependence of scattered intensity on the scattering direction is represented by the scattering form factor, P(q): In eq 20, q is the scattering vector with modulus q ) (4π/λ)sin(θ s /2), where λ is the radiation wavelength and θ s is the angle subtended by the scattering direction and the prolongation of the incident beam. The integration extends to all the pairs of points within the particle, with position vectors r 1 and r 2 .…”

Section: Theorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Scattering of light or other electromagnetic radiation is capable of monitoring such changes because changes in scattering intensity reflect change in the distribution of conformations. Indeed, the technique of electric field light scattering has been experimentally investigated, , although its use is not widespread. Light scattering in flows is also an interesting possibility. , In this paper, we use the theoretical formalism developed in a previous work 14 for describing deformation and scattering intensities and apply it to semiflexible macromolecules.…”

Section: Introductionmentioning

confidence: 99%

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Birefringence, Deformation, and Scattering of Wormlike Macromolecules under an External Agent. Steady-State Properties in an Electric Field

2003

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In this paper, we study the steady-state birefringence, deformation, and scattering of wormlike macromolecules under the influence of an electric field. We use a model of N + 1 pointlike elements whose connectors define N axially symmetric subunits. The model is able to describe some properties of segmentally flexible and wormlike macromolecules depending on the choice of N. We use the Monte Carlo computer simulation technique to characterize the effect of the electric field on the orientation and deformation of molecules with permanent and induced dipoles. Using this technique, we study the effect of the field in different models with the same flexibility (defined as 〈s2〉0/〈s2〉0,str). Orientation is studied through changes in birefringence and deformation through changes in the gyration tensor of the molecule. When the behavior of a broken rod (typical case of segmental flexibility) and a wormlike chain is compared, the differences are generally quantitative although significant enough to be used to obtain information about the internal structure of a macromolecule.

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“…Such changes could be monitored by scattering of light or other electromagnetic radiation. Indeed, the technique of electric-field light scattering has been experimentally investigated, , although it is not in widespread use. Light scattering in flows is also an interesting possibility. , In any case, scattering intensity changes reflect the change in the distribution of conformations.…”

Section: Introductionmentioning

confidence: 99%

Birefringence, Deformation, and Scattering of Segmentally Flexible Macromolecules under an External Agent. Steady-State Properties in an Electric Field

et al. 1999

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Segmentally flexible macromolecules are composed of a few rigid subunits joined by semiflexible joints. When such macromolecules are exposed to an external agent, they become oriented and deformed, and this fact can be monitored by birefringence and scattering. In this paper, we present a theoretical treatment of deformation and scattering of segmentally flexible macromolecules in an external agent that complements existing treatments of birefringence. We treat in detail the case in which the external agent is an electric field, particularizing for the case of a macromolecule with two cylindrically symmetric subunits. We focus on the steady-state behavior of the molecule in the field, studying the effect of arbitrarily high field strengths, which can be simulated using a Monte Carlo procedure. We show how the dependence of birefringence and deformation on field strength can be related to the electrooptical properties of the macromolecule and its flexibility. Particular attention is paid to macromolecular deformation expressed in term of the gyration tensor, whose components can be determined from separate scattering experiments with different scattering geometries. A joint discussion of deformations and birefringence provides a nexus between the techniques of electric birefringence and electric-field light scattering.

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Light Scattering in Electric Fields

Cited by 4 publications

References 43 publications

Transient electric birefringence of wormlike macromolecules in electric fields of arbitrary strength: A computer simulation study

Transient electric birefringence of wormlike macromolecules in electric fields of arbitrary strength: A computer simulation study

Birefringence, Deformation, and Scattering of Wormlike Macromolecules under an External Agent. Steady-State Properties in an Electric Field

Birefringence, Deformation, and Scattering of Segmentally Flexible Macromolecules under an External Agent. Steady-State Properties in an Electric Field

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