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This study revisits the electroabsorption (EA) spectrum of polyacetylene, (CH)x thin-films, for both the cis- and trans-isomers, 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 material’s 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 scattering (RS) spectrum. In contrast, the EA spectrum of trans-(CH)x does not match the first derivative of the material’s absorption spectrum, and the phonon sideband frequency does not agree with the RS spectrum. In addition, the EA spectrum of trans-(CH)x reveals a band below the first allowed 1Bu exciton. We interpret this feature as due to the electric field activated even-parity dark (forbidden) exciton, namely mAg (m>2), showing that the ‘non-luminescent’ trans-(CH)x is due to the reverse order of the excited states, where a series of dark mAg exciton lies below the allowed 1Bu 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 1Bu to mAg influences the apparent frequency that determines the phonon sideband. Consequently, from the EA and RS spectra we estimate the 1Bu lifetime in trans-(CH)x to be ~30 fs. Moreover, the integrated EA spectrum of trans-(CH)x shows a traditional Huang-Rhys type series with a relaxation parameter, S ~ 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 film’s chain lengths distribution. This is due to the N3 response of the non-linear susceptibility, (3) (~EA), dependence on the chain length having N monomers. 

Spin waves, quantized as magnons, have low energy loss and magnetic damping, which are critical for devices based on spin‐wave propagation needed for information processing devices. The organic‐based magnet [V(TCNE)x; TCNE = tetracyanoethylene; x ≈ 2] has shown an extremely low magnetic damping comparable to, for example, yttrium iron garnet (YIG). The excitation, detection, and utilization of coherent and non‐coherent spin waves on various modes in V(TCNE)x is demonstrated and show that the angular momentum carried by microwave‐excited coherent spin waves in a V(TCNE)x film can be transferred into an adjacent Pt layer via spin pumping and detected using the inverse spin Hall effect. The spin pumping efficiency can be tuned by choosing different excited spin wave modes in the V(TCNE)x film. In addition, it is shown that non‐coherent spin waves in a V(TCNE)x film, excited thermally via the spin Seebeck effect, can also be used as spin pumping source that generates an electrical signal in Pt with a sign change in accordance with the magnetization switching of the V(TCNE)x. Combining coherent and non‐coherent spin wave detection, the spin pumping efficiency can be thermally controlled, and new insight is gained for the spintronic applications of spin wave modes in organic‐based magnets. 

Using a combination of two-dimensional infrared (2D IR) and variable temperature Fourier transform infrared (FTIR) spectroscopies the rapid structural isomerization of a five-coordinate ruthenium complex is investigated. In methylene chloride, three exchanging isomers were observed: (1) square pyramidal equatorial, ( 1 ); (2) trigonal bipyramidal, ( 0 ); and (3) square pyramidal apical, ( 2 ). Exchange between 1 and 0 was found to be an endergonic process (Δ H = 0.84 (0.08) kcal mol −1 , Δ S = 0.6 (0.4) eu) with an isomerization time constant of 4.3 (1.5) picoseconds (ps, 10 −12 s). Exchange between 0 and 2 however was found to be exergonic (Δ H = −2.18 (0.06) kcal mol −1 , Δ S = −5.3 (0.3) eu) and rate limiting with an isomerization time constant of 6.3 (1.6) ps. The trigonal bipyramidal complex was found to be an intermediate, with an activation barrier of 2.2 (0.2) kcal mol −1 and 2.4 (0.2) kcal mol −1 relative to the equatorial and apical square pyramidal isomers respectively. This study provides direct validation of the mechanism of Berry pseudorotation – the pairwise exchange of ligands in a five-coordinate complex – a process that was first described over fifty years ago. This study also clearly demonstrates that the rate of pseudorotation approaches the frequency of molecular vibrations.