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The rotational anisotropy of a molecule in a constrained environment is modeled by wobbling-in-a-cone (WIAC) motion, which describes the angular space sampled by the molecule. Recent polarization-selective IR pump–probe measurements have applied this model to phenylselenocyanate in amorphous polymers, aiming to probe the surrounding free volume. A faster rotational timescale was hypothesized to reflect the angular space within the static voids of the polymer matrix, while a slower timescale relates to constraint release by the polymer backbones. To better quantify the contributions of internal bond rotation and polymer segmental motion, we conduct molecular dynamics simulations on two phenylselenocyanate variants with different internal rotational barriers, as well as on p-chlorobenzonitrile, which lacks such internal rotational freedom, within a polymer matrix. Our analyses reveal that the faster (∼10 ps) component of the cyano group's anisotropy decay arises from concurrent angular sampling due to internal bond rotation and WIAC motion. Conversely, polymer segmental motion was found to have a minimal influence on the slow (∼200 ps) anisotropy component. Based on these findings, we refine the WIAC model to better link rotational diffusion with the distinct free volume elements accessed by the probe molecule. This revised model allows the quantification of free volume elements associated with both internal bond rotation and wobbling motion within the polymer cage. [ABSTRACT FROM AUTHOR]

The stability of high‐energy‐density lithium metal batteries (LMBs) heavily relies on the composition of the solid electrolyte interphase (SEI) formed on lithium metal anodes. In this study, the inorganic‐rich SEI layer was achieved by incorporating bisalts additives into carbonate‐based electrolytes. Within this SEI layer, the presence of LiF, polythionate, and Li3N was observed, generated by combining 1.0 м lithium bis(trifluoromethanesulfonyl)imide in ethylene carbonate: ethyl methyl carbonate:dimethyl carbonate in a 1 : 1 : 1 volume ratio, with the addition of 2 wt% lithium difluorophosphate and 2 wt% lithium difluoro(oxalato)borate additives (EL‐DO). Furthermore, this formulation effectively mitigated corrosion of aluminum current collectors. EL‐DO exhibited outstanding performance, including an average coulombic efficiency of 98.2 % in Li||Cu cells and a stable discharge capacity of approximately 162 mAh g−1 after 200 cycles in a Li||LiNi0.8Co0.1Mn0.1O2 (NCM811) configuration. Moreover, EL‐DO displayed the potential to enhance the performance not only of LMBs but also of lithium‐ion batteries. In the case of Gr||NCM811 cell using EL‐DO, it consistently maintained high discharge capacities, even achieving around 135 mAh g−1 after the 100th cycle, surpassing the performance of other electrolytes. This study underscores the synergistic impact of bisalts additives in elevating the performance of lithium batteries. [ABSTRACT FROM AUTHOR]

The infrared (IR) probe often suffers from an unexpected complex absorption profile due to the Fermi resonance and short vibrational lifetime, which restricts the application of time-resolved IR spectroscopy to investigate the site-specific structural dynamics of the protein. Researchers have found that isotope substitution to the IR probe not only removes the Fermi resonance but also extends the dynamic observation window with a prolonged vibrational lifetime. This method has been successfully applied to modify the vibrational properties of many IR probes for time-resolved spectroscopy and imaging. In this study, the effect of isotope substitution (15N) on the vibrational properties of the azide stretching band in 4-azido-L-phenylalanine has been investigated using ultrafast pump-probe and 2D-IR spectroscopy. In contrast to the earlier reports, it has been observed that the Fermi resonance remains unchanged even after isotope substitution, and there is very little change in the vibrational relaxation dynamics as well. Anharmonic frequency analysis reveals that the α-N atom of N3 is being shared between the two transitions participating in the Fermi resonance and gets affected similarly due to isotope labeling. Hence, this study unveils the specific circumstance at which the isotope labeling strategy may not be successful in eliminating the Fermi resonance band and explains the molecular origin behind it. This study also suggests definitive approaches on how to overcome the limitations related to the Fermi resonance to extend the development and application of this IR probe for biological research. [ABSTRACT FROM AUTHOR]