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1. Mechanisms of Complete Dissociation of CO ₂ on Iron Clusters

   https://doi.org/10.1002/cphc.202200277  

   Gutsev, Gennady_L; Tibbetts, Katharine_M; Gutsev, Lavrenty_G; Aldoshin, Sergey_M; Ramachandran, Bala_R (August 2022, ChemPhysChem)

   Abstract Dissociation of CO₂on iron clusters was studied by using semilocal density functional theory and basis sets of triple‐zeta quality. Fe₂, Fe₄, and Fe₁₆clusters were selected as the representative host clusters. When searching for isomers of Fe_nCO₂,n=2, 4 and 16 corresponding to carbon dioxide attachment to the host clusters, its reduction to O and CO, and to the complete dissociation, it was found that the total spin magnetic moments of the lowest energy states of the isomers are often quenched with respect to those of initial reagents Fe_n+CO₂. Dissociation pathways of the Fe₂+CO₂, Fe₄+CO₂, and Fe₁₆+CO₂reactions contain several transition states separated by the local minima states; therefore, a natural question is where do the spin flips occur? Since lifetimes of magnetically excited states were shown to be of the order of 100 fs, the search for the CO₂dissociation pathways was performed under the assumption that magnetic deexcitation may occur at the intermediate local minima. Two dissociation pathways were obtained for each Fe_n+CO₂reaction using the gradient‐based methods. It was found that the Fe₂+CO₂reaction is endothermic with respect to both reduction and complete dissociation of CO₂, whereas the Fe₄+CO₂and Fe₁₆+CO₂reactions are exothermic to both reduction and complete dissociation of carbon dioxide. The CO₂reduction was found to be more favorable than its complete dissociation in the Fe₄case. 

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2. Vibrational spectroscopy and dissociation dynamics of cyclohexyl hydroperoxide

   https://doi.org/10.1039/D4SC00151F  

   Roy, Tarun Kumar; Qian, Yujie; Karlsson, Elizabeth; Rabayah, Rawan; Sojdak, Christopher A; Kozlowski, Marisa C; Karsili, Tolga_N V; Lester, Marsha I (April 2024, Chemical Science)

   Vibrational spectroscopy and dissociation dynamics of a prototypical cyclic hydroperoxide, cyclohexyl hydroperoxide has been studied using a combination of synthesis, spectroscopy, and theoretical methods. 

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3. Exciton dissociation in quantum dots connected with photochromic molecule bridges

   https://doi.org/10.1039/D1TC04451F  

   Yoon, Lucy U.; Adhikari, Surya B.; Sarabamoun, Ephraiem S.; Bietsch, Jonathan M.; Tsai, Esther H.; Wang, Guijun; Choi, Joshua J. (November 2021, Journal of Materials Chemistry C)

   We report modulation of exciton dissociation dynamics in quantum dots (QD) connected with photochromic molecules. Our results show that switching the configuration of photochromic molecules changes the inter-QD potential barrier height which has a major impact on the charge tunnelling and exciton dissociation. The switching of the dominant exciton decay pathway between the radiative recombination and exciton dissociation results in switchable photoluminescence intensity from QDs. Implications of our findings for optical memory and optical computing applications are discussed. 

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4. Tracking ultrafast non-adiabatic dissociation dynamics of the deuterated water dication molecule

   https://doi.org/10.1063/5.0219029  

   Iskandar, W; Rescigno, T N; Orel, A E; Larsen, K A; Severt, T; Streeter, Z L; Jochim, B; Griffin, B; Call, D; Davis, V; et al (July 2024, The Journal of Chemical Physics)

   We applied reaction microscopy to elucidate fast non-adiabatic dissociation dynamics of deuterated water molecules after direct photo-double ionization at 61 eV with synchrotron radiation. For the very rare D+ + O+ + D breakup channel, the particle momenta, angular, and energy distributions of electrons and ions, measured in coincidence, reveal distinct electronic dication states and their dissociation pathways via spin–orbit coupling and charge transfer at crossings and seams on the potential energy surfaces. Notably, we could distinguish between direct and fast sequential dissociation scenarios. For the latter case, our measurements reveal the geometry and orientation of the deuterated water molecule with respect to the polarization vector that leads to this rare 3-body molecular breakup channel. Aided by multi-reference configuration-interaction calculations, the dissociation dynamics could be traced on the relevant potential energy surfaces and particularly their crossings and seams. This approach also unraveled the ultrafast time scales governing these processes. 

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5. Dissociation slowdown by collective optical response under strong coupling conditions

   https://doi.org/10.1063/5.0133972  

   Sukharev, Maxim; Subotnik, Joseph; Nitzan, Abraham (February 2023, The Journal of Chemical Physics)

   We consider an ensemble of diatomic molecules resonantly coupled to an optical cavity under strong coupling conditions at normal incidence. Photodissociation dynamics is examined via direct numerical integration of the coupled Maxwell–Schrödinger equations with molecular rovibrational degrees of freedom explicitly taken into account. It is shown that the dissociation is significantly affected (slowed down) when the system is driven at its polaritonic frequencies. The observed effect is demonstrated to be of transient nature and has no classical analog. An intuitive explanation of the dissociation slowdown at polaritonic frequencies is proposed. 

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