Excited states

  • Article
    | Open Access

    Understanding the source of vibrationally excited molecular hydrogen is an essential prerequisite for understanding the chemical evolution in the universe. Here the authors report a photodissociation pathway to produce vibrationally excited H2 via the water photochemistry.

    • Yao Chang
    • , Feng An
    •  & Xueming Yang
  • Article
    | Open Access

    Commonly, large π-conjugated systems facilitate low-energy electronic transitions. Here, the authors demonstrate that the relief of excited-state antiaromaticity of the benzene core leads to large Stokes shifts, and allows the construction of emitters covering the entire visible spectrum without the need of extending π-conjugation.

    • Heechan Kim
    • , Woojin Park
    •  & Dongwhan Lee
  • Article
    | Open Access

    A complete understanding of singlet fission (SF) in molecular materials will enable the design of optimised optoelectronic devices. Here, the authors use vacancy control in acene-based blends to link coherent and incoherent SF pathways to energetics.

    • Clemens Zeiser
    • , Chad Cruz
    •  & Katharina Broch
  • Article
    | Open Access

    Radiationless relaxation is ubiquitous in natural processes and often involves excited states that are difficult to observe. Here the authors, combining X-ray transient absorption spectroscopy and computations, provide insight into the photoinduced dynamics in pyrazine and the involvement of an optically dark 1Au(nπ*) state.

    • Valeriu Scutelnic
    • , Shota Tsuru
    •  & Stephen R. Leone
  • Article
    | Open Access

    The use of room temperature exciton–polariton Bose–Einstein condensation is limited by the need for external high-finesse microcavities. The authors generate room temperature EPs with single-crystal microribbons as waveguide Fabry–Pérot microcavities, and demonstrate controllable output of coherent light.

    • Ji Tang
    • , Jian Zhang
    •  & Yong Sheng Zhao
  • Article
    | Open Access

    The primary energy conversion step in photosynthesis, charge separation, takes place in the reaction center. Here the authors investigate the heliobacterial reaction center using multispectral two-dimensional electronic spectroscopy, identifying the primary electron acceptor and revealing the charge separation mechanism.

    • Yin Song
    • , Riley Sechrist
    •  & Jennifer P. Ogilvie
  • Article
    | Open Access

    Three-body dissociation of water, producing one oxygen and two hydrogen atoms, has been difficult to investigate due to the lack of intense vacuum ultraviolet sources. Here, using a tunable free-electron laser, the authors obtain quantum yields for this channel showing that it is a possible route to prebiotic oxygen formation in interstellar environments.

    • Yao Chang
    • , Yong Yu
    •  & Xueming Yang
  • Article
    | Open Access

    Optical pulses can be useful to create and control molecules in higher quantum states. Here the authors use optical pumping to create rotationally excited states of SiO+ molecular ion into super rotor ensemble.

    • Ivan O. Antonov
    • , Patrick R. Stollenwerk
    •  & Brian C. Odom
  • Article
    | Open Access

    Exploiting delocalized organic polaritons for enhanced exciton harvesting has been advantageous for organic optoelectronic with planar heterojunctions. Here, the authors report polariton-assisted excitation energy channeling in organic heterojunctions coupled to the same cavity mode.

    • Mao Wang
    • , Manuel Hertzog
    •  & Karl Börjesson
  • Article
    | Open Access

    Two-dimensional perovskite shows potential for optoelectronic applications due to its large exciton binding energy, yet the exciton-phonon interaction with the polar soft lattice is not well-understood. Here, the authors reveal the intermediate coupling regime where exciton polarons are momentarily trapped by lattice vibrations.

    • Weijian Tao
    • , Chi Zhang
    •  & Haiming Zhu
  • Article
    | Open Access

    The dissociation mechanism of the heme axial ligand in heme proteins is not yet fully understood. The authors investigate the photodissociation dynamics of the bond between heme Fe and methionine S in ferrous cytochrome c using femtosecond time-resolved X-ray solution scattering and X-ray emission spectroscopy, simultaneously tracking electronic and nuclear structure changes.

    • Marco E. Reinhard
    • , Michael W. Mara
    •  & Kelly J. Gaffney
  • Article
    | Open Access

    Activation of narrow-bandgap photocatalysts holds key to applicable solar-to-hydrogen energy conversion. Here, the authors demonstrate effective sequential cocatalyst decoration for such narrow-bandgap photocatalysts to realise highly-efficient hydrogen evolution and Z-scheme water splitting.

    • Zheng Wang
    • , Ying Luo
    •  & Kazunari Domen
  • Article
    | Open Access

    Colloidal CdSe nanocrystals hold great promise in applications due to their tunable optical spectrum. Using hybrid time-dependent density functional theory, the authors show that colloidal CdSe nanocrystals are inherently defective with a low energy spectrum dominated by dark, surface-associated excitations.

    • Tamar Goldzak
    • , Alexandra R. McIsaac
    •  & Troy Van Voorhis
  • Perspective
    | Open Access

    Photon-induced charge separation phenomena are at the heart of light-harvesting applications but challenging to be described by quantum mechanical models. Here the authors illustrate the potential of machine-learning approaches towards understanding the fundamental processes governing electronic excitations.

    • Florian Häse
    • , Loïc M. Roch
    •  & Alán Aspuru-Guzik
  • Article
    | Open Access

    Eumelanin protects cells from sun damage and is promising for energy conversion applications, but its structure and excited state dynamics are elusive. Here the authors shed light on both aspects combining selective excitation of UV- and visible-absorbing chromophores with time-resolved infrared spectroscopy.

    • Christopher Grieco
    • , Forrest R. Kohl
    •  & Bern Kohler
  • Article
    | Open Access

    The identification of molecular quantum states becomes challenging with increasing complexity of the molecular level structure. Here, the authors non-destructively identified excited molecular states of the $${{\rm{N}}}_{2}^{+}$$ N 2 + by interfering forces applied to both the molecular ion and to a co-trapped atomic ion.

    • Kaveh Najafian
    • , Ziv Meir
    •  & Stefan Willitsch
  • Article
    | Open Access

    Photoreceptor UVR8 in plants senses environmental UV levels through 26 structural tryptophan residues, but the role of 18 of them was unknown. The authors show, by experiments and computations, how these form a light-harvesting network that funnels the excitation to the pyramid centers enhancing the light-perception efficiency.

    • Xiankun Li
    • , Haisheng Ren
    •  & Dongping Zhong
  • Article
    | Open Access

    The change from low-spin hexacoordinated to high-spin pentacoordinated domed form in heam upon ligand detachment and the reverse process underlie the respiratory function. The authors, using femtosecond time-resolved X-ray emission spectroscopy, capture the transient states connecting the two forms in myoglobin-NO upon NO photoinduced detachment.

    • Dominik Kinschel
    • , Camila Bacellar
    •  & Majed Chergui
  • Article
    | Open Access

    The mechanisms of formation of the (6-4) photoproducts in DNA damage by sunlight is still debated. Here the authors show, by optical spectroscopies and computations, the details of the formation of a (6-4) photoadduct via the thietane intermediate in a single-stranded DNA oligonucleotide.

    • Luis A. Ortiz-Rodríguez
    • , Christian Reichardt
    •  & Carlos E. Crespo-Hernández
  • Article
    | Open Access

    Excited-state structural and electronic changes, observed in molecules, are hampered in nanomaterials. Here the authors identify structural distortion and electron redistribution in three photoexcited gold nanoclusters, connecting molecular and nanocrystal regimes, enabled by flexibility of the tetrahedral core units.

    • Qi Li
    • , Dongming Zhou
    •  & Rongchao Jin
  • Article
    | Open Access

    Resolving concerted nuclear and electronic motion in real-time is a primary goal in chemistry. The authors monitor nuclear and valence electronic dynamics in the excited state single-bond isomerisation of a chromophore of photoactive yellow protein, using time-resolved photoelectron imaging and electronic structure calculations.

    • Cate S. Anstöter
    • , Basile F. E. Curchod
    •  & Jan R. R. Verlet
  • Article
    | Open Access

    OLED materials based on thermally activated delayed fluorescence have promising efficiency. Here, the authors investigate an organometallic multicore Cu complex as luminophore, by pump-probe X-ray techniques at three different facilities deriving a complete picture of the charge transfer in the triplet excited state.

    • Grigory Smolentsev
    • , Christopher J. Milne
    •  & Matthias Vogt
  • Article
    | Open Access

    Photoabsorption is a fundamental process that leads to changes in the electron density in matter. Here, the authors show a direct measurement of the distribution of electron density when a cyclohexadine molecule is excited by pulsed UV radiation and probed by a time delayed X-ray pulse generated at LCLS.

    • Haiwang Yong
    • , Nikola Zotev
    •  & Peter M. Weber
  • Article
    | Open Access

    Symmetric multibranched donor-acceptor molecules are promising photoactive materials for diverse applications. Here the authors show that, in octupolar and quadrupolar dyes, excited-state symmetry breaking occurs efficiently in polar solvents only and results in a concentration of the excitation that may trigger fast photochemical reactions.

    • Bogdan Dereka
    • , Denis Svechkarev
    •  & Eric Vauthey
  • Article
    | Open Access

    Circular polarization luminescence (CPL) spectroscopy is a tool to study chiroptical systems, but the measurement process is generally very slow. The authors introduce a CPL technique with much faster acquisition, demonstrating meaningful time-dependent measurements and enabling new applications.

    • Lewis E. MacKenzie
    • , Lars-Olof Pålsson
    •  & Robert Pal
  • Article
    | Open Access

    Sulfur is abundant in the Universe, but the observed abundance ratio of SH to H2S doesn’t agree with astrochemical models. The authors measure product state-resolved translational energy spectra of photoproducts in a jet-cooled H2S beam as a function of wavelength, showing that SH yield is lower than assumed in the models.

    • Jiami Zhou
    • , Yarui Zhao
    •  & Xueming Yang
  • Article
    | Open Access

    Electron spin is a fundamental property of molecules, and changes in spin state affect both molecular structure and dynamics. Here, the authors resolve, by ultrafast electron diffraction, the nuclear reorganization stabilizing spin transitions in a [FeII(bpy)3](PF6)2 crystal.

    • Yifeng Jiang
    • , Lai Chung Liu
    •  & R. J. Dwayne Miller
  • Article
    | Open Access

    A steep absorption edge is preferred for high performance solar cells, but is less common for organic solar cells (OSCs). Here Panhans et al. find that the absorption tails are dominated by zero point vibrations and are responsible for the lowering of the open-circuit voltage and the performance of OSCs.

    • Michel Panhans
    • , Sebastian Hutsch
    •  & Frank Ortmann
  • Article
    | Open Access

    The lifetime of decaying quantum states has been thought to depend on the strength of the coupling causing the decay. Here the authors demonstrate that quantum mechanical interference can dominate this process, observing Fano-Feshbach resonance lifetimes covering several orders of magnitude.

    • Alexander Blech
    • , Yuval Shagam
    •  & Christiane P. Koch
  • Article
    | Open Access

    Long-standing radical species have raised noteworthy concerns in organic chemistry and but there remains a substantial challenge to produce long-standing radicals by light. Here, the authors demonstrate a stable dithienylethene derived photochromic radical for detection of peroxides and ozone.

    • Xuanying Chen
    • , Wandong Zhao
    •  & Liangliang Zhu
  • Article
    | Open Access

    Photoactive biomolecules rely on chromophores whose photochemistry depends on the environment. Here, the excited state dynamics of a model for the anionic biochromophore in photoactive yellow protein is investigated by time-resolved photoelectron spectroscopy showing involvement of a non-valence state, and lack of E-Z isomerisation in the gas phase.

    • James N. Bull
    • , Cate S. Anstöter
    •  & Jan R. R. Verlet
  • Article
    | Open Access

    Energy transfer in light harvesting complexes involves electronic, vibrational, and vibronic couplings which are challenging to resolve. Here the authors observe the time-evolution of vibronic coherences driving charge transfer in a photoexcited solvated transition metal complex by two- and three-dimensional electronic-vibrational spectroscopy.

    • James D. Gaynor
    • , Jason Sandwisch
    •  & Munira Khalil
  • Article
    | Open Access

    Excited state aromaticity gives rise to unique photophysical properties which may aid the design of functional photoactive materials. Here, the authors spectroscopically characterize an acceptor-donor-acceptor system featuring a two-electron transfer process stabilized by aromatization in the lower energy excited state.

    • Jinseok Kim
    • , Juwon Oh
    •  & Dongho Kim
  • Article
    | Open Access

    Antimony trisulfide has a proper bandgap of 1.7 eV for making solar cells but the devices suffer from severe voltage loss. Here Yang et al. propose that the photoexcited carriers are self-trapped by lattice deformation, which places a thermodynamic limit of only 0.8 V for the open circuit voltage.

    • Zhaoliang Yang
    • , Xiaomin Wang
    •  & Haiming Zhu
  • Article
    | Open Access

    Ultrafast photo-induced processes in complex systems require theoretical models and their experimental validation which are still lacking. Here the authors investigate singlet fission in a pentacene dimer by a combined experimental and theoretical approach providing a real-time visualisation of the process.

    • Christoph Schnedermann
    • , Antonios M. Alvertis
    •  & Andrew J. Musser
  • Article
    | Open Access

    Many animals use the Earth’s magnetic field for orientation, yet the underlying principles are poorly understood. The authors show that a molecular triad acts as a chemical compass in magnetic fields of similar magnitude to that of the Earth, supporting the hypothesis that photo-initiated quantum processes underlie bird magnetoreception.

    • Christian Kerpal
    • , Sabine Richert
    •  & Christiane R. Timmel
  • Article
    | Open Access

    Transition metals are at the basis of key processes in chemistry and biology but their complex electronic structures make understanding of their properties a challenge. Here the authors resolve individual spectral lines of Cu2 in the deep UV region by two-colour resonant four-wave mixing.

    • M. Beck
    • , P. Bornhauser
    •  & P. P. Radi
  • Article
    | Open Access

    Molecular systems displaying aggregation-induced emission (AIE) have important biomedical and optoelectronic applications. Here the authors report a further mechanism for AIE, through aromaticity reversal from the ground state to the excited state, in the non-aromatic annulene derivative of cyclooctatetrathiophene.

    • Zheng Zhao
    • , Xiaoyan Zheng
    •  & Ben Zhong Tang
  • Article
    | Open Access

    The potential of organic materials with persistent room-temperature phosphorescence for high-tech application is limited by their low efficiency. Here, the authors report a strategy to enhance persistent room-temperature phosphorescence efficiency via intramolecular triplet-triplet energy transfer.

    • Weijun Zhao
    • , Tsz Shing Cheung
    •  & Ben Zhong Tang
  • Article
    | Open Access

    Free electron lasers provide a state-of-the-art tool to investigate the photochemistry of water. Here, the authors show that highly rotationally excited hydroxyl radicals, so-called “super rotors” existing above the bond dissociation energy, are observed from the photodissociation of water, which may have implications for understanding the interstellar medium.

    • Yao Chang
    • , Yong Yu
    •  & Xueming Yang
  • Article
    | Open Access

    Rydberg atoms can be created from photoexcitation of molecules using intense ultrafast laser pulses. Here the authors use a coincidence detection of electrons, ion and excited Rydberg atoms and their energy sharing to reveal the general mechanism of Rydberg state excitation in a dissociating H2 molecule.

    • Wenbin Zhang
    • , Xiaochun Gong
    •  & Jian Wu
  • Article
    | Open Access

    Here, the authors explore the ultrafast photodynamics of methyl anthranilate. From the quantum beat behavior, the authors find evidence for ultrafast energy redistribution processes which hinder excited state relaxation, making methyl anthranilate a poor choice for a sunscreen chemical filter.

    • Natércia d. N. Rodrigues
    • , Neil C. Cole-Filipiak
    •  & Vasilios G. Stavros
  • Article
    | Open Access

    Interatomic or intermolecular Coulombic decay is responsible for the generation of slow electrons in clusters and biological samples. Here the authors use electron–electron coincidence detection to find the competitive roles of proton transfer and ICD that occur on similar time scales in water clusters.

    • Clemens Richter
    • , Daniel Hollas
    •  & Uwe Hergenhahn