Ultrafast Transient Spectroscopy of Trans-Polyacetylene in the Midinfrared Spectral Range
Artikel i vetenskaplig tidskrift, 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 π-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 ∼1.5  eV having similar polarization memory. The primary excitons undergo internal conversion within ∼100  fs to an even-parity (dark) singlet exciton with a PA band at ∼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.

Photoexcitation

Ultrafast pump-probe spectroscopy

Excitons

Conducting polymers

Författare

C. X. Sheng

School of Electronic and Optical Engineering, Nanjing University of Science and Technology, Nanjing, Jiangsu 210094, China

Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112, USA

Kyung Ho Kim

Chalmers, Mikroteknologi och nanovetenskap (MC2), Kvantkomponentfysik

Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea

M. Tong

Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112, USA

C. Yang

Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112, USA

H. Kang

Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea

Yung Woo Park

Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA

Institute of Applied Physics, Seoul National University, Seoul 08826, Korea

Z. V. Vardeny

Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112, USA

Physical Review Letters

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

Vol. 124 1 017401

Ämneskategorier

Polymerkemi

Fysik

Kemi

DOI

10.1103/PhysRevLett.124.017401

Mer information

Senast uppdaterat

2020-02-14