Theory of the time development of the stokes shift in polar media

Bagchi, Biman; Oxtoby, David W.; Fleming, Graham R.

doi:10.1016/0301-0104(84)80014-2

Cited by 399 publications

(300 citation statements)

References 25 publications

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“…Second, a corresponding dynamical relation between the Fourier transform in Eq. 2 and the complex dielectric function є(ω) is obtained within a quasistatic approximation [13,14]. The sampleinduced non-contact friction is related to the polymer dielectric function by…”

Section: Nih Public Accessmentioning

confidence: 99%

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Dielectric Fluctuations and the Origins of Noncontact Friction

2006

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Dielectric fluctuations underlie a wide variety of physical phenomena, from ion mobility in electrolyte solutions and decoherence in quantum systems to dynamics in glass-forming materials and conformational changes in proteins. Here we show that dielectric fluctuations also lead to noncontact friction. Using high sensitivity, custom fabricated, single crystal silicon cantilevers we measure energy losses over poly(methyl methacrylate), poly(vinyl acetate), and polystyrene thin films. A new theoretical analysis, relating non-contact friction to the dielectric response of the film, is consistent with our experimental observations. This work constitutes the first direct, mechanical detection of friction due to dielectric fluctuations.The fundamental relationship between random forces and friction plays a pivotal role in physics, chemistry, and biology. Surprisingly, the origin of force fluctuations and friction between objects in close proximity, but not in physical contact, remains poorly understood. Such non-contact friction is important in a variety of seemingly disparate fields, including micro-and nanomechanics, trapped ions for quantum computation, and measurements of quantum gravitation at small length scales. The non-contact friction measurements reported here are motivated by recent advances in the mechanical detection of magnetic resonance [1,2]; the sensitivity in these measurements has so far been limited by non-contact friction between a cantilever tip and the sample surface [3].The advent of high sensitivity single crystal silicon cantilevers [4,5] provides a new opportunity to elucidate the mechanisms of non-contact friction. These cantilevers' combination of low spring constant and low intrinsic losses enable the detection of non-contact friction with unprecedented sensitivity. Initial work on non-contact friction using high sensitivity cantilevers by Stipe et. al measured dissipation using a conducting probe over metal and quartz substrates at tip-sample separations down to 2 nm and temperatures from 4 -300K [3]. Friction over Au (111) was found to be 7 orders of magnitude larger than predicted by Coulomb drag theories [6]; several alternative mechanisms have been suggested [7][8][9]. In this Letter we explore noncontact friction over polymer films.A single high-sensitivity silicon cantilever was used as shown in Fig. 1(a). The cantilever approached the surface in a perpendicular orientation to avoid snap-in to contact [4] and the motion of the cantilever was parallel to the surface. The cantilever was 250m long, 5m wide, and 340 nm thick, with a spring constant k = 7 × 10 −4 N/m, a fundamental resonance frequency ω c /2π = 7.385 kHz, and a quality factor Q = 31000 ( Fig. 1(b)) [5]. The tip region of the cantilever has been thinned from 340 nm to < 100 nm using a reactive ion etch. The cantilever tip has a radius of ~ 30nm and has been coated with a thin layer of platinum using a shadow mask technique [4].We measure the total friction Γ t by recording the cantilever ringdown time τ, Fig. 1(c...

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Section: Nih Public Accessmentioning

confidence: 99%

“…3 thus rests on two approximations: linear response theory for the dielectric, and the adiabatic treatment [13,14] of dielectric fluctuations.…”

Section: Nih Public Accessmentioning

confidence: 99%

Dielectric Fluctuations and the Origins of Noncontact Friction

2006

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“…In a simple Debye continuum model [49], one predicts a single exponential decay with a time constant % = '/'1 = '/'D" ¢',z¢//I[0 , where T o is the (transverse) Debye relaxation time, z I is the longitudinal relaxation time and e~ and ~0 are the dielectric constants at infinite and zero frequency, respectively. In more sophisticated models the solvation dynamics can be highly nonexponential, but, especially when the translation of the solvent molecules is included, the magnitude of the average relaxation time approaches that for z 1 [50].…”

Section: Picosecond Transientsmentioning

confidence: 99%

Picosecond time-dependent Stokes shift studies of fluoroprobe in liquid solution

et al. 1995

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We report on a picosecond spectroscopic study of the dynamical Stokes shift of fluoroprobe in the lowest excited state in the solvents diethylether and ethylacetate. Time-resolved emission spectra with a time-resolution of approximately 10 ps are presented. The spectra reflect dynamical Stokes shifts of a few thousand wave numbers within 10-100 ps after the pulsed laser excitation. The time-dependent shifts are representative of the solvation dynamics of fluoroprobe in diethylether and ethylacetate.

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“…Several reviews have appeared in literature on various aspects of dynamics of interfacial water [1,[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33].…”

Section: Introductionmentioning

confidence: 99%

Hydrogen bonds of interfacial water in human breast cancer tissue compared to lipid and DNA interfaces

Abramczyk¹,

Brożek-Płuska²,

Surmacki³

et al. 2011

JBPC

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The paper presents the results for water confined in a human breast cancerous tissue, a single stranded DNA, a double stranded DNA and in phospholipids (DPPC-D--Phosphatidylcholine, dipalmitoyl). The interfacial water in DNA and lipids is represented by a double band in the region of the OH stretching mode of water corresponding to the symmetric and asymmetric vibrational modes, in contrast to water confined in the cancerous breast tissue where only one band at 3311 cm -1 has been recorded. The marked red-shift of the maximum peak position of the OH stretching mode confirms that the vibrational properties of the interfacial water observed in restricted biological environment differ drastically from those in bulk water. The change of vibrational pattern of behavior may be due to the decoupling of the vibrations of the OH bonds in water molecule or change of the vibrational selection rules at biological interfaces. According to our knowledge Raman vibrational properties of water confined in the normal and cancerous breast tissue of the same patient have not been reported in literature yet. Here we have also presented the first Raman 'optical biopsy' images of the non-cancerous and cancerous (infiltrating ductal cancer) human breast tissues.

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Theory of the time development of the stokes shift in polar media

Cited by 399 publications

References 25 publications

Dielectric Fluctuations and the Origins of Noncontact Friction

Dielectric Fluctuations and the Origins of Noncontact Friction

Picosecond time-dependent Stokes shift studies of fluoroprobe in liquid solution

Hydrogen bonds of interfacial water in human breast cancer tissue compared to lipid and DNA interfaces

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