Low-energy vibrational modes in phenylene oligomers studied by THz time-domain spectroscopy

Johnston, Michael B.; Herz, Laura M.; Khan, Amena L. T.; Köhler, Anna; Davies, A. G.; Linfield, E. H.

doi:10.1016/s0009-2614(03)01136-9

Cited by 94 publications

(43 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A wide range of organic and bio-organic materials in the form of such pellets has been studied in the THz region, including explosives materials 1 and their by-products, 2 conjugated oligomers, 3 amino acids, 4 and DNA. 5 While much spectroscopic information can be obtained from pellet samples, in many cases their THz spectra exhibit broad line shapes due to intrinsic line broadening mechanisms, and to effects related to pellet preparation.…”

mentioning

confidence: 99%

Line narrowing of terahertz vibrational modes for organic thin polycrystalline films within a parallel plate waveguide

Melinger

Laman

Harsha

et al. 2006

Applied Physics Letters

View full text Add to dashboard Cite

Waveguide terahertz time-domain spectroscopy is used to demonstrate the narrowing of vibrational lines for a thin polycrystalline film of 1,2-dicyanobenzene in a parallel plate metal waveguide. When compared to corresponding linewidths for 1,2-dicyanobenzene in a pellet sample at room temperature, the linewidths for the waveguide film are found to be significantly sharper. For measurements near 77 K, a dramatic line narrowing is observed for the waveguide film, yielding linewidths as much as five times sharper than found in the pellet. These effects are attributed to much smaller inhomogeneous broadening in the waveguide film and result in a more informative spectrum. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2405884͔A standard method for measuring terahertz ͑THz͒ spectra of organic solids is to form a pellet that contains a small quantity of the target solid dispersed in a much larger quantity of a low absorbance host material such as polyethylene. A wide range of organic and bio-organic materials in the form of such pellets has been studied in the THz region, including explosives materials 1 and their by-products, 2 conjugated oligomers, 3 amino acids, 4 and DNA. 5 While much spectroscopic information can be obtained from pellet samples, in many cases their THz spectra exhibit broad line shapes due to intrinsic line broadening mechanisms, and to effects related to pellet preparation. 6 A promising method for investigating the THz properties of organic solids is through the use of THz waveguides. 7-9 For waveguide terahertz timedomain spectroscopy ͑THz-TDS͒ the parallel plate metal waveguide ͑PPWG͒ is particularly useful because of the nondispersive and low loss propagation for the transverse electromagnetic mode. 7,9 The high detection sensitivity that is possible with the PPWG has recently been demonstrated by the THz-TDS characterization of nanometer thick water layers. 9 In addition, the PPWG is easily opened, and the exposed flat inner surfaces are ideal for coating with a thin film of the investigated material.In this letter we demonstrate the application of a PPWG to the terahertz TDS characterization of a solid organic thin polycrystalline film. The material 1,2-dicyanobenzene ͑12DCB͒ is studied because of its relatively strong vibrational lines in the THz region. 10 The major finding of this study is that the THz spectrum of a waveguide polycrystalline film can display significantly sharper vibrational linewidths than found in the corresponding THz spectrum of the pellet. For measurements performed near 77 K, a dramatic line narrowing was observed for the waveguide film, yielding linewidths as much as five times sharper than found in the pellet sample. The line narrowing effect revealed additional vibrational structure in the waveguide film which is not apparent in the pellet. We attribute the line narrowing to a reduction of inhomogeneous broadening for the 12DCB polycrystalline film drop cast on the metal waveguide surface. We also demonstrate the high sensitivity of the waveguide techniq...

show abstract

mentioning

confidence: 99%

Line narrowing of terahertz vibrational modes for organic thin polycrystalline films within a parallel plate waveguide

Melinger

Laman

Harsha

et al. 2006

Applied Physics Letters

View full text Add to dashboard Cite

show abstract

“…Many molecular crystals have phonon resonances in the THz domain. [1][2][3][4][5] The ability to measure small quantities of these materials will depend on the strength of the absorption lines and on the value of the corresponding refractive-index. For an absorption coefficient of ∼500 cm −1 , an order-of-magnitude estimate for many molecular crystal resonances in the THz domain, a layer of tens of microns thickness may be required to obtain a measurable effect on the absorption.…”

Section: Resultsmentioning

confidence: 99%

“…[1][2][3][4][5] One of the problems with standard THz spectroscopy, however, is that diffraction limits the size of the smallest samples for which a spectrum can be measured, to values of a few hundred micrometers or more. When a crystal is much smaller than this, light simply diffracts around it and in the far-field, little or no information about the crystal can be extracted from the measured THz electric field.…”

Section: Introductionmentioning

confidence: 99%

Terahertz near-field spectroscopy of filled subwavelength sized apertures in thin metal films

Knab¹,

Adam²,

Shaner³

et al. 2013

Opt. Express

View full text Add to dashboard Cite

Abstract:We have measured terahertz near-field spectra of cesium iodide crystals as small as ∼10 μm in diameter, which were deposited on single, sub-wavelength-sized apertures created in thin gold films on a substrate. The advantage of using small apertures for terahertz microspectroscopy is that only terahertz light that has interacted with the cesium iodide is observed. We find that around the transverse optical phonon frequency of cesium iodide, the amplitude transmission is as much influenced by the refractive index as by the absorption. We show that the ability to measure in the near-field of the apertures, where signals are relatively strong, allows us to measure on sample volumes as small as ∼5×10 −16 m 3 .

show abstract

“…THz subwavelength microscopes are potentially highly interesting for biological applications, although this probably requires expanding the useful frequency range of these devices to higher THz frequencies where resonances of biological molecules in solution are plentiful. At lower THz frequencies (<5 THz), these microscopes can, however, be used to measure lattices resonances of small molecular crystals, which do show characteristic spectroscopic fingerprints in this frequency region [19][20][21]. With one exception, [15], THz sub-wavelength micro-spectroscopy has not been demonstrated yet, perhaps because at low terahertz frequencies even lattice resonances of molecular crystals are weak compared to their counterparts at high THz frequencies.…”

Section: Introductionmentioning

confidence: 99%

THz near-field measurements of metal structures

Adam

Brok

Planken

et al. 2008

Comptes Rendus. Physique

View full text Add to dashboard Cite

Low-energy vibrational modes in phenylene oligomers studied by THz time-domain spectroscopy

Cited by 94 publications

References 26 publications

Line narrowing of terahertz vibrational modes for organic thin polycrystalline films within a parallel plate waveguide

Line narrowing of terahertz vibrational modes for organic thin polycrystalline films within a parallel plate waveguide

Terahertz near-field spectroscopy of filled subwavelength sized apertures in thin metal films

THz near-field measurements of metal structures

Contact Info

Product

Resources

About