Exciton Surface Polaritons Research Articles

ChemInform Abstract: EXPERIMENTAL AND THEORETICAL STUDY OF EXCITON SURFACE POLARITONS ON ORGANIC CRYSTALS. II. HIGHLY REFLECTING FACES OF CTIP AND PTS

Chemischer InformationsdienstVolume 11, Issue 30 Physical Organic Chemistry ChemInform Abstract: EXPERIMENTAL AND THEORETICAL STUDY OF EXCITON SURFACE POLARITONS ON ORGANIC CRYSTALS. II. HIGHLY REFLECTING FACES OF CTIP AND PTS M. R. PHILPOTT, M. R. PHILPOTTSearch for more papers by this authorI. POCKRAND, I. POCKRANDSearch for more papers by this authorA. BRILLANTE, A. BRILLANTESearch for more papers by this authorJ. D. SWALEN, J. D. SWALENSearch for more papers by this author M. R. PHILPOTT, M. R. PHILPOTTSearch for more papers by this authorI. POCKRAND, I. POCKRANDSearch for more papers by this authorA. BRILLANTE, A. BRILLANTESearch for more papers by this authorJ. D. SWALEN, J. D. SWALENSearch for more papers by this author First published: July 29, 1980 https://doi.org/10.1002/chin.198030042AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume11, Issue30July 29, 1980 RelatedInformation

Experimental and theoretical study of exciton surface polaritons on organic crystals. II. Highly reflecting faces of CTIP and PTS

Exciton surface polaritons have been observed at room temperature on the highly reflecting crystal faces of CTIP [γ-cyclopropyl-bis (1,3,3-trimethylindolenine-2-yl)pentamethinium fluoroborate] and PTS [poly-2,4-hexadiyne-1,6-diol bis (p-toluene sulfonate)]. These surface modes, which cannot be excited by light incident from air, were detected by measuring the attenuated total reflection (ATR) of a focused laser beam inside a prism separated from the crystal face by a gap of the order of the wavelength of the exciting light. The experimental dispersion curves of the surface modes were obtained by plotting the photon energy against the angle of the reflectance minimum. The surface active component of the complex dielectric tensor was calculated for both cyrstals and found to agree quite well with values obtained from normal incidence reflectivity studies. Several supporting theoretical studies are also reported, including: (i) the calculation of the free exciton surface polariton dispersion curves for the natural faces of CTIP, (ii) model calculations representing the ATR for all energies and angles as a perspective figure, and (iii) an investigation of the stop-point region where the virtual exciton surface polariton intersects the volume polariton modes of the CTIP crystal.

Optical surface polariton spectroscopy of organic crystals and monolayer assemblies

Two types of experiments involving surface polaritons are described. In the first the dispersions ω vs. k of exciton surface polaritons (ESP's) on three highly reflecting organic solids have been determined at room temperature. In the second back-bending in the dispersion curve of a plasmon surface polariton (PSP) on silver covered with a monolayer of dye molecules, is attributed to exciton-surface plasmon interactions.

Exciton transitions in quasi-one-dimensional crystals. 9-Cyanoanthracene

The polarized reflection spectra of 9-cyanoanthracene crystal at 2 °K taken at near normal angles of incidence are reported for a wavelength range corresponding to the first singlet electronic transition. The dielectric funtion is calculated by means of the Kramers–Kronig transformation and the positions and oscillator strengths of the main exciton transitions are located. The factor group splitting in reflection is nearly 80 cm−1, but in the derived absorption spectrum ε2(ω) the splitting is much larger, being approximately 200 cm−1. One component of the dielectric function is negative in the region of the 0–0 transition and the calculation of the theoretical attenuated total reflection spectrum suggests that at 2 °K the (100) crystal surface should support an exciton surface polariton. The structure of the exciton band has been calculated for three orthogonal directions in the first Brillouin zone using the point dipole approximation. All four branches show strong negative dispersion in the kc direction, implying that the bottom of the exciton band is not a k=0 level. This is one reason why the crystal shows no ’’monomer’’ fluorescence. The qualitative validity of the point dipole model has been established by calculating the nondipolar part of the exciton transfer interaction for near neighbors. It is found that the nondipolar parts are 25% or less of the individual intermolecular exciton transfer interactions.

Experimental and theoretical study of exciton surface polaritons on organic crystals. I. (010) face of TCNQ ° single crystals

An exciton surface polariton has been observed at room temperature by the technique of attenuated total reflection (ATR) spectroscopy on the (010) face of tetracyanoquinodimethane (TCNQ °) single crystals. From the p-polarized reflectivity as a function of the angle of incidence at constant wavelength, the experimental dispersion of the surface mode and the real and imaginary part of the dielectric function were determined in the wavelength region 515–425 nm. Supporting theoretical studies also reported include a calculation of the dispersion curve of a free exciton surface polariton, the calculation of perspective figures representing the ATR at fixed prism-crystal gaps for variable frequency and angle of incidence, and the calculation of the intensity of the electromagnetic field in the prism, gap and the crystal.

Observation of exciton surface polaritons at room temperature

Exciton surface polaritons have been detected by the technique of attenuated total reflection at 295 K on the (110) surface of the organic dye crystal γ-cyclopropyl-bis (,3,3-trimethyl-indoline-2-yl) pentamethinium tetrafluoroborate. This is the first time that an exciton surface polariton has been reported at room temperature on any material. The dispersion of the surface polariton was determined in the range 1.95 eV to 2.81 eV by measuring the change in the p-polarized reflectivity with angle at fixed wavelength.

Exciton surface polaritons on organic crystals

Exciton surface polaritons (ESP’s) are electromagnetic waves which are localized at solid surfaces and have exponentially decaying electric fields on either side of the interface. They are nonradiative, that is, they cannot be excited by photons incident on a plane surface, but they can be excited by an evanescent wave from a prism coupler not in contact with the surface for angles of incidence beyond the critical. We have identified some organic solids that could support these modes at optical and near ultraviolet wavelengths at room temperature. Calculations are presented of the attenuated total reflectivity as a function of angle of incidence at wavelengths within the polariton stop band of the solids. In addition calculations of the intensity of the electromagnetic field in the prism, gap, and sample are given to illustrate the resonance enhancement of the field intensity at the crystal surface when the ESP is excited.

Experimental observation of exciton surface polaritons on a polymerized diacetylene crystal

Exciton surface polaritons (ESP's) have been observed by the technique of attenuated total reflection (ATR) spectroscopy at 295 K on the (100) face of the polymerized diacetylene crystal poly-2,4-hexadiyne-1,6-diol bis ( p-toluene sulfonate). The ATR experiments were performed by measuring the p-polarized reflectivity as a function of angle of incidence at constant wavelength. By changing the wavelength of the exciting light and repeating the angular scans, the experimental dispersion of the surface mode was determined for the wavelength range 632.8 to 596 nm. The intensity of the electromagnetic field in the three regions, prism, gap and sample, was calculated to demonstrate the localization of the ESP at the crystal surface.