The Dispersion Effect of Resonance Raman Lines in trans-Polyacetylene

Kuzmany, H.; Knöll, P.

doi:10.1007/978-3-642-82569-9_19

Cited by 9 publications

(5 citation statements)

References 22 publications

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“…Resonance Raman studies of “polyacetylene” [ 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 ] make use of the fact that Raman scattering under resonance conditions has a greatly enhanced contribution from species that have electronic excitation resonances near the Raman excitation frequency. If the sample is homogeneous, then the intensity of vibrational features in the resonance Raman spectrum will all increase or decrease together as the excitation frequency is changed.…”

Section: Review Of Experimental Observations On Polyacetylene Withmentioning

confidence: 99%

“…This is because the one-electron excitation involved does not result in a significant geometry change for a system of effectively infinite size. The most argumentative statement of the issue is in [ 46 ], in which it is claimed that (a) since “polyacetylene” has a well-known Raman spectrum, it must be the case that something is missing that is beyond the Condon scattering mechanism; (b) a vibronic activity term is added (called B-term scattering), which (c) explains (“solving polyacetylene”) by addition of the next term albeit with an unknown magnitude, and (d) that this refinement also removes the need to consider polyacetylene as a heterogeneous mixture of finite chains [ 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 ]. Specifically, quoting from [ 46 ], “In ref.…”

Section: Review Of Experimental Observations On Polyacetylene Withmentioning

confidence: 99%

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Polyacetylene: Myth and Reality

Hudson

2018

Materials

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Polyacetylene, the simplest and oldest of potentially conducting polymers, has never been made in a form that permits rigorous determination of its structure. Trans polyacetylene in its fully extended form will have a potential energy surface with two equivalent minima. It has been assumed that this results in bond length alternation. It is, rather, very likely that the zero-point energy is above the Peierls barrier. The experimental studies that purport to show bond alternation are reviewed and shown to be compromised by serious experimental inconsistencies or by the presence, for which there is considerable evidence, of finite chain polyenes. In this view, addition of dopants results in conductivity by facilitation of charge transport between finite polyenes. The double minimum potential that necessarily occurs for polyacetylene, if viewed as the result of elongation of finite chains, originates from admixture of the 11Ag ground electronic state with the 21Ag excited electronic singlet state. This excitation is diradical (two electron) in character. The polyacetylene limit is an equal admixture of these two 1Ag states making theory intractable for long chains. A method is outlined for preparation of high molecular weight polyacetylene with fully extended chains that are prevented from reacting with neighboring chains.

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Section: Review Of Experimental Observations On Polyacetylene Withmentioning

confidence: 99%

Section: Review Of Experimental Observations On Polyacetylene Withmentioning

confidence: 99%

Polyacetylene: Myth and Reality

Hudson

2018

Materials

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show abstract

“…Resonance Raman studies of "polyacetylene" [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46] make use of the fact that Raman scattering under resonance conditions has a greatly enhanced contribution from species that have electronic excitation resonances near the Raman excitation frequency. If the sample is homogeneous, then the intensity of vibrational features in the resonance Raman spectrum will all increase or decrease together as the excitation frequency is changed.…”

Section: Resonance Raman Spectroscopymentioning

confidence: 99%

“…This is because the one-electron excitation involved does not result in a significant geometry change for a system of effectively infinite size. The most argumentative statement of the issue is in [46], in which it is claimed that (a) since "polyacetylene" has a well-known Raman spectrum, it must be the case that something is missing that is beyond the Condon scattering mechanism; (b) a vibronic activity term is added (called B-term scattering), which (c) explains ("solving polyacetylene") by addition of the next term albeit with an unknown magnitude, and (d) that this refinement also removes the need to consider polyacetylene as a heterogeneous mixture of finite chains [31][32][33][34][35][36][37][38][39][40][41][42]. Specifically, quoting from [46], "In ref.…”

Section: Resonance Raman Spectroscopymentioning

confidence: 99%

Double minimum potential of polyacetylene: Consequences of ignoring

Hudson¹

2020

Preprint

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Polyacetylene, the simplest and oldest of potentially conducting polymers, has never been made in a form that permits rigorous determination of its structure. Trans polyacetylene in its fully extended form will have a potential energy surface with two equivalent minima. It has been assumed that this results in bond length alternation. It is, rather, very likely that the zero-point energy is above the Peierls barrier. The experimental studies that purport to show bond alternation are reviewed and shown to be compromised by serious experimental inconsistencies or by the presence, for which there is considerable evidence, of finite chain polyenes. In this view, addition of dopants results in conductivity by facilitation of charge transport between finite polyenes. The double minimum potential that necessarily occurs for polyacetylene, if viewed as the result of elongation of finite chains, originates from admixture of the 1 1 A g ground electronic state with the 2 1 A g excited electronic singlet state. This excitation is diradical (two electron) in character. The polyacetylene limit is an equal admixture of these two 1 A g states making theory intractable for long chains. A method is outlined for preparation of high molecular weight polyacetylene with fully extended chains that are prevented from reacting with neighboring chains.

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“…В спектрах всех пленок наблюдается максимум с частотой, близкой к 1050 см −1 , который называют T -пиком, как наблюдалось в работе [35], но он был обнаружен только при возбуждении в УФ области. Мы можем наблюдать полосу с частотой ∼ 1470 см −1 , которая в литературных данных описывалась как характерная только для пленок, состоящих из углеродных шаров [36], или для трансполимера (CC-мода растяжения), частоты 1078 и 1458 см −1 [37]. Для аморфного углерода характерна широкая полоса с центром 1480 см −1 [38].…”

Section: метод расчетаunclassified

Анализ Структуры И Проводимости Изогнутых Цепочек Углерода, Полученных Методом Импульсного Плазменного Осаждения На Различных Металлических Подложках

Иваненко¹,

Краснощеков²,

Павликов³

2018

Физика И Техника Полупроводников

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Пленки линейно-цепочечного углерода толщиной порядка 100 нм изучались методом туннельной спектроскопии. Обнаружена осциллирующая зависимость дифференциальной проводимости исследуемых структур. Полученные результаты интерпретировались с использованием модели формирования волн зарядовой плотности в регулярных изгибах структуры углеродных цепочек. Получены спектры комбинационного рассеяния пленок. Проведено теоретическое соотнесение моделированных спектров гармонических колебаний полиинов (−C≡C−)n и кумуленов (=C=)n углеродных пленок.

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The Dispersion Effect of Resonance Raman Lines in trans-Polyacetylene

Cited by 9 publications

References 22 publications

Polyacetylene: Myth and Reality

Polyacetylene: Myth and Reality

Double minimum potential of polyacetylene: Consequences of ignoring

Анализ Структуры И Проводимости Изогнутых Цепочек Углерода, Полученных Методом Импульсного Плазменного Осаждения На Различных Металлических Подложках

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