Jaspal Singh Bola, Ryan M. Stolley, Prashanna Poudel, Joel S. Miller, Christoph Boheme, Z. Valy Vardeny
{"title":"暗激子对聚乙炔电吸收光谱的影响","authors":"Jaspal Singh Bola, Ryan M. Stolley, Prashanna Poudel, Joel S. Miller, Christoph Boheme, Z. Valy Vardeny","doi":"arxiv-2405.03012","DOIUrl":null,"url":null,"abstract":"This study revisits the electroabsorption (EA) spectrum of polyacetylene, as\nfunctions of the electric field strength, isomerization degree, and light\npolarization states. The EA spectrum of $cis$-$(CH)_x$ reveals an oscillatory\nfeature that follows the Stark shift-related first derivative of the materials\nabsorption spectrum that contains v(0-1) and v(0-2) sidebands of the excited\n$C=C$ stretching vibration that agrees well with the Raman spectrum. EA\nspectrum of $trans $-$(CH)_x$ does not match the first derivative of the\nmaterials absorption spectrum, and the phonon sideband frequency does not agree\nwith the RS spectrum. EA spectrum of $trans $-$(CH)_x$ reveals a band below the\nfirst allowed $1B_u$ exciton. We interpret this feature as due to the electric\nfield activated even-parity dark (forbidden) exciton, namely $mA_g$ ($m >1$),\nshowing that the nonluminescent $trans $-$(CH)_x$ is due to the reverse order\nof the excited states, where a dark $mA_g$ exciton lies below the allowed\n$1B_u$ exciton. This agrees with the unusual phonon sideband in $trans\n$-$(CH)_x$ absorption, since the excited state attenuation caused by the fast\ninternal conversion from $1B_u$ to $mA_g$ influences the apparent frequency\nthat determines the phonon sideband. Consequently, from the EA and RS spectra\nwe estimate the $1B_u$ lifetime in $trans $-$(CH)_x$ to be $\\sim 30$ fs.\nIntegrated EA spectrum of $trans $-$(CH)_x$ shows a traditional Huang-Rhys type\nseries with a relaxation parameter, $S \\sim 0.5$. This indicates that the EA\nspectrum of the $trans $ isomer is also determined by a Stark shift related to\nthe first derivative of the absorption spectrum, but preferentially for the\nlongest chains in the films chain lengths distribution. This is due to the\n$N^3$ response of the non-linear susceptibility, $\\chi^{(3)}$ ($\\sim$EA),\ndependence on the chain length having $N$ monomers.","PeriodicalId":501211,"journal":{"name":"arXiv - PHYS - Other Condensed Matter","volume":"49 1","pages":""},"PeriodicalIF":0.0000,"publicationDate":"2024-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"The influence of dark excitons on the electroabsorption spectrum of polyacetylene\",\"authors\":\"Jaspal Singh Bola, Ryan M. Stolley, Prashanna Poudel, Joel S. Miller, Christoph Boheme, Z. Valy Vardeny\",\"doi\":\"arxiv-2405.03012\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"This study revisits the electroabsorption (EA) spectrum of polyacetylene, as\\nfunctions of the electric field strength, isomerization degree, and light\\npolarization states. The EA spectrum of $cis$-$(CH)_x$ reveals an oscillatory\\nfeature that follows the Stark shift-related first derivative of the materials\\nabsorption spectrum that contains v(0-1) and v(0-2) sidebands of the excited\\n$C=C$ stretching vibration that agrees well with the Raman spectrum. EA\\nspectrum of $trans $-$(CH)_x$ does not match the first derivative of the\\nmaterials absorption spectrum, and the phonon sideband frequency does not agree\\nwith the RS spectrum. EA spectrum of $trans $-$(CH)_x$ reveals a band below the\\nfirst allowed $1B_u$ exciton. We interpret this feature as due to the electric\\nfield activated even-parity dark (forbidden) exciton, namely $mA_g$ ($m >1$),\\nshowing that the nonluminescent $trans $-$(CH)_x$ is due to the reverse order\\nof the excited states, where a dark $mA_g$ exciton lies below the allowed\\n$1B_u$ exciton. This agrees with the unusual phonon sideband in $trans\\n$-$(CH)_x$ absorption, since the excited state attenuation caused by the fast\\ninternal conversion from $1B_u$ to $mA_g$ influences the apparent frequency\\nthat determines the phonon sideband. Consequently, from the EA and RS spectra\\nwe estimate the $1B_u$ lifetime in $trans $-$(CH)_x$ to be $\\\\sim 30$ fs.\\nIntegrated EA spectrum of $trans $-$(CH)_x$ shows a traditional Huang-Rhys type\\nseries with a relaxation parameter, $S \\\\sim 0.5$. This indicates that the EA\\nspectrum of the $trans $ isomer is also determined by a Stark shift related to\\nthe first derivative of the absorption spectrum, but preferentially for the\\nlongest chains in the films chain lengths distribution. This is due to the\\n$N^3$ response of the non-linear susceptibility, $\\\\chi^{(3)}$ ($\\\\sim$EA),\\ndependence on the chain length having $N$ monomers.\",\"PeriodicalId\":501211,\"journal\":{\"name\":\"arXiv - PHYS - Other Condensed Matter\",\"volume\":\"49 1\",\"pages\":\"\"},\"PeriodicalIF\":0.0000,\"publicationDate\":\"2024-05-05\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"arXiv - PHYS - Other Condensed Matter\",\"FirstCategoryId\":\"1085\",\"ListUrlMain\":\"https://doi.org/arxiv-2405.03012\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"\",\"JCRName\":\"\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"arXiv - PHYS - Other Condensed Matter","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/arxiv-2405.03012","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
The influence of dark excitons on the electroabsorption spectrum of polyacetylene
This study revisits the electroabsorption (EA) spectrum of polyacetylene, as
functions of the electric field strength, isomerization degree, and light
polarization states. The EA spectrum of $cis$-$(CH)_x$ reveals an oscillatory
feature that follows the Stark shift-related first derivative of the materials
absorption spectrum that contains v(0-1) and v(0-2) sidebands of the excited
$C=C$ stretching vibration that agrees well with the Raman spectrum. EA
spectrum of $trans $-$(CH)_x$ does not match the first derivative of the
materials absorption spectrum, and the phonon sideband frequency does not agree
with the RS spectrum. EA spectrum of $trans $-$(CH)_x$ reveals a band below the
first allowed $1B_u$ exciton. We interpret this feature as due to the electric
field activated even-parity dark (forbidden) exciton, namely $mA_g$ ($m >1$),
showing that the nonluminescent $trans $-$(CH)_x$ is due to the reverse order
of the excited states, where a dark $mA_g$ exciton lies below the allowed
$1B_u$ exciton. This agrees with the unusual phonon sideband in $trans
$-$(CH)_x$ absorption, since the excited state attenuation caused by the fast
internal conversion from $1B_u$ to $mA_g$ influences the apparent frequency
that determines the phonon sideband. Consequently, from the EA and RS spectra
we estimate the $1B_u$ lifetime in $trans $-$(CH)_x$ to be $\sim 30$ fs.
Integrated EA spectrum of $trans $-$(CH)_x$ shows a traditional Huang-Rhys type
series with a relaxation parameter, $S \sim 0.5$. This indicates that the EA
spectrum of the $trans $ isomer is also determined by a Stark shift related to
the first derivative of the absorption spectrum, but preferentially for the
longest chains in the films chain lengths distribution. This is due to the
$N^3$ response of the non-linear susceptibility, $\chi^{(3)}$ ($\sim$EA),
dependence on the chain length having $N$ monomers.