Article
Chemistry, Multidisciplinary
Jenny Triptow, Andre Fielicke, Gerard Meijer, Mallory Green
Summary: Photoelectron Circular Dichroism (PECD) is a forward-backward asymmetry in photoemission induced by circularly polarized light. PECD spectroscopy using anions allows for mass-selectivity and simple experimental schemes with table-top light sources. However, limited evidence and understanding exist for PECD in anions. This study demonstrates the PECD effect in mass-selected deprotonated 1-indanol anions and observes similar PECD values to neutral species.
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
(2023)
Article
Chemistry, Physical
Cate S. Anstoter, Jan R. R. Verlet
Summary: Photographing the pyramidal sulphite radical monoanion in the photon energy range of 3.10-4.45 eV revealed two features corresponding to the formation of the ground electronic state of the neutral and thermionic emission. Vibrational structures associated with the umbrella mode of the neutral were observed in the photoelectron spectra and angular distributions. The observed thermionic emission was attributed to the excitation of degenerate Feshbach resonances that can internally convert and statistically emit electrons.
Article
Engineering, Multidisciplinary
M. Ranke, S. Walther, T. Gebert, A. Dimitriou, M. Sumfleth, M. J. Prandolini, M. Wieland, M. Drescher, U. Fruehling
Summary: The translation introduces a design of a velocity map imaging (VMI) spectrometer with a novel gas capillary integrated into the repeller electrode, allowing direct supply of target gas without degrading resolution. This design achieves high gas density and a large aperture for focusing long wavelength radiation into the VMI spectrometer, facilitating time resolved experiments with intense terahertz (THz) light fields. The spectrometer's performance is demonstrated through momentum maps of electrons from multiphoton ionization of xenon and a first extreme ultraviolet-THz-streak experiment.
MEASUREMENT SCIENCE AND TECHNOLOGY
(2021)
Article
Multidisciplinary Sciences
Zhengbo Qin
Summary: Recently, the photoelectron angular distribution of pseudohalide CN- has been directly demonstrated to be comparable to Cl- using the photoelectron velocity map imaging technique. Despite having similar high electron affinity and strong chemical bonding capabilities, their photoelectron angular distributions are distinctly different, indicating their different electronic-structure symmetry. This work provides a method for explaining the photoelectron angular distributions of pseudohalide and classic halide ligands using advanced photoelectron velocity map imaging tool.
Article
Chemistry, Applied
Jumei Zhang, Zhiling Liu, Gang Li, Hongjun Fan, Ling Jiang, Hua Xie
Summary: The study investigated the reactions of CO molecules with several heterobinuclear transition metal-iron clusters and found the formation of thermodynamically stable MFe(CO)(4-) complexes that activated CO molecules.
JOURNAL OF ENERGY CHEMISTRY
(2021)
Article
Chemistry, Physical
Chris Sparling, Alice Ruget, Nikoleta Kotsina, Jonathan Leach, Dave Townsend
Summary: This study demonstrates the successful application of artificial neural networks (ANNs) for removing Poissonian noise in charged particle imaging measurements, achieving impressive performance in processing multiphoton ionization images and producing reliable data similar to benchmark references. The potential impact of using ANNs in the widespread use of charged particle imaging methods within the chemical dynamics community is highlighted, particularly in handling very low absorption/photoionization cross-sections and extracting subtle image features.
Article
Chemistry, Applied
Yu Zhang, Shihu Du, Zhi Zhao, Haiyan Han, Gang Li, Jinghan Zou, Hua Xie, Ling Jiang
Summary: Metal carbides play a significant role in catalysis and functional materials, but the structural characterization of metal carbide clusters is challenging. In this study, size-specific photoelectron velocity-map imaging spectroscopy is used to investigate the structures and properties of platinum carbide clusters. Quantum chemical calculations are conducted to identify the structures and assign the experimental spectra. The results indicate that the cluster size where a chain-to-ring structural evolution occurs is n = 14 for PtCn- anions and n = 10 for PtCn neutrals, highlighting the significant impact of charge on the structures of metal carbides. The findings also emphasize the preference of platinum atoms to expose on the outer side of the chain or ring, serving as active sites for potential catalytic reactions. These spectroscopic snapshots provide insights into the formation and growth of platinum carbide clusters, and have implications for the development of single-atom catalysts with isolated metal atoms on supports.
JOURNAL OF ENERGY CHEMISTRY
(2023)
Article
Chemistry, Physical
Yair Yifrach, Joshua H. Baraban, Ilana Bar
Summary: This study demonstrates a new spatial imaging technique, KESMI, which can recover kinetic energy and angular momentum information in photophysical processes using a VMI system in different out of-focus modes. The analysis of characteristic stripes in KESMI profiles allows breakthrough developments of a global model that enables understanding and analysis of these features. Furthermore, the derivation of PE velocity distribution from the ionization of a single H2O quantum state provides further evidence of the feasibility of this new approach.
JOURNAL OF PHYSICAL CHEMISTRY A
(2022)
Article
Chemistry, Physical
Chiyan Liu, Jian Liu, Yong Han, Zhangrui Wang, Hui Zhang, Xiaoming Xie, Bo Yang, Zhi Liu
Summary: The hydration process of a Nafion membrane was studied using ambient-pressure x-ray photoelectron spectroscopy (APXPS), which provided a quantitative analysis of water content and the transformation of sulfonic acid groups. The conductivity of the membrane was determined by electrochemical impedance spectroscopy, establishing a connection between the electrical properties and the microscopic mechanism. Ab initio molecular dynamics simulations provided core-level binding energies of O- and S-containing species in the Nafion + H2O system.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Environmental Sciences
Mohamadhasan Mohamadian Sarvandani, Emanuel Kastle, Lapo Boschi, Sylvie Leroy, Mathilde Cannat
Summary: p, he create qqosp or eder rp。
Article
Spectroscopy
Zhenhang Jin, Jiangle Zhang, Shanjun Chen, Yan Chen, Weibing Zhang, Zaifa Shi, Jingxiong Yu, Song Li, Zichao Tang, Zhengbo Qin
Summary: The study investigated the structural and electronic properties of HoO- using photoelectron imaging spectroscopy and ab initio calculations. The research obtained the ADE and VDE of HoO, and performed Franck-Condon simulation to determine the vibrational structure and spectral bands in the photoelectron spectrum.
SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY
(2021)
Article
Instruments & Instrumentation
Chuan Cheng, Goenenc Mogol, Thomas Weinacht, Andrei Nomerotski, Carlos Trallero-Herrero
Summary: In this study, we demonstrate three-dimensional velocity map imaging of low energy electrons using a TPX3CAM. The position and timing information on the camera sensor encode the three-dimensional momentum information [p(x), p(y), p(z)]. By employing a constant fraction discriminator and fast time to digital converter in the camera, we can accurately capture the time information. We showcase the capabilities of our apparatus through above threshold ionization measurements of xenon, which reveal distinct structures in the momentum-resolved photoelectron yield.
REVIEW OF SCIENTIFIC INSTRUMENTS
(2022)
Article
Physics, Atomic, Molecular & Chemical
Asim Kumar Das, Rishabh Tripathi, Aparna Shastri, Sunanda Krishnakumar, N. Bhargava Ram, B. N. Rajasekhar
Summary: Femtosecond laser based multiphoton ionization experiments were conducted for the first time on dialkyl carbonate green solvent molecules, namely dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate (DMC, DEC, EMC). The dissociation products resulting from ionization were investigated by detecting electrons and ions using velocity map imaging technique in coincidence mode. By comparing the mass spectra of DMC, DEC, and EMC, possible mechanisms involving direct bond cleavage as well as isomerization and reorganization to generate the final dissociation products were proposed. The measured photoelectron kinetic energy release distributions in coincidence with various fragment ions correlated with the possible fragmentation pathways and were compared for all three molecules, confirming the proposed mechanisms. Additionally, experimental estimates for the ionization potentials of DEC and EMC, which have not been reported before, were obtained.
INTERNATIONAL JOURNAL OF MASS SPECTROMETRY
(2022)
Article
Chemistry, Physical
Schuyler P. Lockwood, Ricardo B. Metz
Summary: The bond strength and photodissociation dynamics of MgI+ are studied using theory, photodissociation spectroscopy, and photofragment velocity map imaging. The photodissociation spectrum of MgI+ shows a broad and unstructured profile from 17,000 to 21,500 cm(-1), with perpendicular anisotropy observed in the photofragment images. Bond dissociation energy is determined to be 203.0 +/- 1.8 kJ/mol (2.10 +/- 0.02 eV) at 17,000 +/- 150 cm(-1). Resonance enhanced two-photon dissociation is observed at photon energies of 33,000-41,000 cm(-1), leading to the formation of exclusively I+ fragments.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Physics, Atomic, Molecular & Chemical
Hanyu Zhang, Lijun Geng, Yuhan Jia, Xin Lei, Zhixun Luo
Summary: A photoelectron velocity-map imaging (VMI) apparatus with a 45-degree plate-set integrated with a time-of-flight mass spectrometer has been developed. This apparatus can capture target cluster anions, change their trajectory, and facilitate ion-extraction, beam focusing, and photoelectron detachment. It not only expands the functionality of the instrument but also maintains compatibility with conventional time-of-flight mass spectrometry.
INTERNATIONAL JOURNAL OF MASS SPECTROMETRY
(2022)
Article
Chemistry, Physical
Marvin N. Pohl, Sebastian Malerz, Florian Trinter, Chin Lee, Claudia Kolbeck, Iain Wilkinson, Stephan Thuermer, Daniel M. Neumark, Laurent Nahon, Ivan Powis, Gerard Meijer, Bernd Winter, Uwe Hergenhahn
Summary: In this study, liquid fenchone's X-ray photoelectron circular dichroism (PECD) at the C 1s edge was experimentally investigated. A new setup that enabled PECD measurements on a liquid microjet was utilized, revealing a non-vanishing asymmetry in the intensity of photoelectron spectra acquired under a fixed angle in the backward-scattering plane for the C 1s line associated with fenchone's carbonyl carbon. This experiment opens up new possibilities for innovative chirality detection of organic/biological molecules in aqueous solutions.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2022)
Article
Chemistry, Physical
Kristina F. Chang, Han Wang, Sonia M. Poullain, Jesus Gonzalez-Vazquez, Luis Banares, David Prendergast, Daniel M. Neumark, Stephen R. Leone
Summary: The photodissociation dynamics of alkyl iodides along the C-I bond were investigated using attosecond extreme-ultraviolet (XUV) transient absorption spectroscopy. The study revealed the wave packet bifurcation at a conical intersection and coherent vibrations in the ground state of the molecules. The observations of coherent vibrations indirectly revealed the structural dynamics of the molecules.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Chemistry, Physical
Chin Lee, Marvin N. Pohl, Isaac A. Ramphal, Walt Yang, Bernd Winter, Bernd Abel, Daniel M. Neumark
Summary: This article presents an experimental setup for studying reactions at gas-liquid interfaces using molecular beam scattering. The setup utilizes a microfluidic chip to create a stable flat liquid sheet and a mass spectrometer to characterize evaporation and scattering from the sheet. The first measurements of evaporation and scattering of dodecane and Ne from flat jets are reported.
JOURNAL OF PHYSICAL CHEMISTRY A
(2022)
Correction
Chemistry, Physical
Masafumi Koga, Megan Asplund, Daniel M. Neumark
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Chemistry, Physical
Masafumi Koga, Megan Asplund, Daniel M. Neumark
Summary: The dynamics of low energy electron attachment to the thio-substituted uracil analog 2-thiouracil were investigated using time-resolved photoelectron spectroscopy. The results showed the formation and decay processes of different anionic states under different excitation energies, as well as the dissociation behavior. Notable differences were observed compared to the related iodide-uracil anion.
JOURNAL OF CHEMICAL PHYSICS
(2022)
Article
Physics, Multidisciplinary
Camila Bacellar, Adam S. Chatterley, Florian Lackner, C. D. Pemmaraju, Rico Mayro P. Tanyag, Deepak Verma, Charles Bernando, Sean M. O. O'Connell, Maximilian Bucher, Ken R. Ferguson, Tais Gorkhover, Ryan N. Coffee, Giacomo Coslovich, Dipanwita Ray, Timur Osipov, Daniel M. Neumark, Christoph Bostedt, Andrey F. Vilesov, Oliver Gessner
Summary: Strong-field ionization of nanoscale clusters provides a unique way to study the complex dynamics of high-density plasmas. By using femtosecond time-resolved x-ray coherent diffractive imaging, the plasma dynamics induced by near-infrared laser in helium droplets with 600 nm diameter were investigated. The observations reveal the establishment of an anisotropic surface region within 100 fs and the subsequent contraction of the dense plasma core at different rates along and perpendicular to the laser polarization.
PHYSICAL REVIEW LETTERS
(2022)
Article
Chemistry, Multidisciplinary
Mark C. Babin, Martin DeWitt, Jascha A. Lau, Marissa L. Weichman, Jongjin B. Kim, Hongwei Song, Hua Guo, Daniel M. Neumark
Summary: The transition state of a chemical reaction, which serves as a dividing surface between reactants and products on the reaction potential energy surface (PES), is of fundamental interest in understanding chemical reactivity. However, its transient nature poses challenges for experimental characterization. In this study, a combination of negative-ion photodetachment-based transition-state spectroscopy and reduced-dimensionality quantum dynamical simulations is used to investigate the F + NH3 → HF + NH2 reaction, revealing detailed vibrational structure associated with the transition state. The study identifies vibrational Feshbach resonances in the product well of the F + NH3 PES and provides insights into the impact of resonances localized across the transition state and reactant complex on the bimolecular reaction dynamics.
Correction
Chemistry, Multidisciplinary
Zachary N. Heim, Daniel M. Neumark
ACCOUNTS OF CHEMICAL RESEARCH
(2023)
Article
Chemistry, Physical
Daniel M. Neumark
Summary: Cryo-SEVI is a high-resolution variant of anion photoelectron spectroscopy that has been successfully applied to the study of radicals, clusters, and transition states. It retains the versatility of conventional anion photoelectron spectroscopy while offering sub-meV resolution to resolve vibrational structure. Recent experiments in our laboratory using cryo-SEVI, including pre-excitation of anions with an infrared laser pulse, are described in this Feature Article.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Chemistry, Physical
Jascha A. Lau, Martin DeWitt, Mark A. Boyer, Mark C. Babin, Tonia Solomis, Max Grellmann, Knut R. Asmis, Anne B. McCoy, Daniel M. Neumark
Summary: High-resolution photoelectron spectra of vibrationally pre-excited vinoxide anions are obtained using the IR-cryo-SEVI technique. The method combines with vibrational perturbation theory to identify anharmonic couplings among vibrational states. The spectra reveal information about the anion and neutral states, including the splitting of the v3 fundamental mode and the estimation of the v5 fundamental frequency.
JOURNAL OF PHYSICAL CHEMISTRY A
(2023)
Article
Multidisciplinary Sciences
Enrico Ridente, Diptarka Hait, Eric A. Haugen, Andrew D. Ross, Daniel M. Neumark, Martin Head-Gordon, Stephen R. Leone
Summary: Understanding the relaxation pathways of photoexcited molecules is crucial for gaining atomistic-level insight into photochemistry. In this study, the geometric relaxation (Jahn-Teller distortion) of the methane cation was investigated using time-resolved attosecond transient absorption spectroscopy. The results revealed that the distortion occurred within a few femtoseconds after strong-field ionization of methane. Coherent oscillations in the vibrational mode of the symmetry-broken cation were activated and detected in the x-ray signal, but damped within a few tens of femtoseconds. This study provides a comprehensive understanding of the molecular relaxation dynamics and has implications for studying complex systems.
Article
Chemistry, Physical
Benjamin W. W. Toulson, Diptarka Hait, Davide Facciala, Daniel M. M. Neumark, Stephen R. R. Leone, Martin Head-Gordon, Oliver Gessner
Summary: The UV photochemistry of small heteroaromatic molecules was studied in this research, which provides insights into fundamental photo-induced chemical transformations in moderately complex compounds. The study focused on the dynamics of 2-iodothiophene (C4H3IS) under 268 nm UV light-induced excitation. Experimental observations and theoretical calculations were combined to understand the relaxation dynamics and dissociation pathway of the molecule. The results showed a pi -> pi* excitation leading to iodine dissociation, followed by fragmentation in a specific bond-length region.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Chemistry, Physical
Walt Yang, Chin Lee, Steven Saric, Marvin N. N. Pohl, Daniel M. M. Neumark
Summary: The evaporation and scattering of Ne, CD4, and D2O from a dodecane flat liquid jet are studied. Translational energy distributions as a function of scattering angle are obtained using a rotatable mass spectrometer. The evaporation experiments reveal a Maxwell-Boltzmann distribution with a cosine angular distribution superimposed on a weak isotropic background. The scattering experiments show contributions from impulsive scattering and thermal desorption. At select incident angles for the three systems, the angular distributions show super-specular scattering for the impulsive scattering channel, attributed to anisotropic momentum transfer to the liquid surface. The impulsive scattering channel is analyzed with a soft-sphere model to explore energy transfer between the scatterer and liquid as a function of deflection angle. Compared to Ne scattering, the polyatomic gases exhibit more thermal desorption and a higher degree of internal excitation in the impulsive scattering channel.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Optics
Nicolette G. Puskar, Yen-Cheng Lin, James D. Gaynor, Maximilian C. Schuchter, Siddhartha Chattopadhyay, Carlos Marante, Ashley P. Fidler, Clare L. Keenan, Luca Argenti, Daniel M. Neumark, Stephen R. Leone
Summary: Attosecond noncollinear four-wave-mixing spectroscopy was used to measure the autoionization decay lifetimes of inner valence electronic excitations in neon atoms. The results show that the lifetimes of 3s, 3p, and 3d states are 7 +/- 2 fs, 48 +/- 8 fs, and 427 +/- 40 fs, respectively. Theoretical calculations verify the experimental findings and provide an assessment of the electron correlation in the autoionization process.
Article
Optics
James D. Gaynor, Ashley P. Fidler, Yuki Kobayashi, Yen-Cheng Lin, Clare L. Keenan, Daniel M. Neumark, Stephen R. Leone
Summary: Attosecond four-wave mixing (FWM) spectroscopy is used to study the Rydberg wave packet dynamics in argon atoms. The experiment shows that the emitted signals from individual Rydberg states have oscillatory structure and persist beyond the expected lifetimes. The coherent amplitude transfer is driven by nonresonant NIR light through dark states during the FWM process.
