Ultrafast Transient Spectroscopy of Trans-Polyacetylene in the Midinfrared Spectral Range
Journal article, 2020

Trans-polyacetylene [t-(CH)(x)] possesses twofold ground state degeneracy. Using the Su-Schrieffer-Heeger Hamiltonian, scientists predicted charged solitons to be the primary photoexcitations in t-(CH)(x); this prediction, however, has led to sharp debate. To resolve this saga, we use subpicosecond transient photomodulation spectroscopy in the mid-IR spectral range (0.1-1.5 eV) in neat t-(CH)(x) thin films. We show that odd-parity singlet excitons are the primary photoexcitations in t-(CH)(x), similar to many other nondegenerate pi-conjugated polymers. The exciton transitions are characterized by two photoinduced absorption (PA) bands at 0.38 and 0.6 eV, and an associated photoluminescence band at similar to 1.5 eV having similar polarization memory. The primary excitons undergo internal conversion within similar to 100 fs to an even parity (dark) singlet exciton with a PA band at similar to 1.4 eV. We also find ultrafast photogeneration of charge polarons when pumping deep into the polymer continuum band, which are characterized by two other PA bands in the mid-IR and associated photoinduced IR vibrational modes.



Ultrafast pump-probe spectroscopy

Conducting polymers


C. X. Sheng

University of Utah

Nanjing University of Science and Technology

Kyung Ho Kim

Chalmers, Microtechnology and Nanoscience (MC2), Quantum Device Physics

Seoul National University

M. Tong

University of Utah

C. Yang

University of Utah

H. Kang

Seoul National University

Y. W. Park

University of Pennsylvania

Seoul National University

Z. V. Vardeny

University of Utah

Physical Review Letters

0031-9007 (ISSN) 1079-7114 (eISSN)

Vol. 124 1 017401

Subject Categories

Atom and Molecular Physics and Optics

Theoretical Chemistry

Condensed Matter Physics





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7/1/2021 6