X-ray Spectroscopy of Liquid Water Microjets

Wilson, Kevin R.; Rude, B.; Catalano, T.; Schaller, Richard D.; Tobin, J. G.; Co, Dick T.; Saykally, Richard J.

doi:10.1021/jp010132u

Cited by 158 publications

(184 citation statements)

References 20 publications

(44 reference statements)

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“…The acidic solution N K-edge spectra are expected to behave identically to the zwitterion. 22 To overcome the technical difficulties inherent in studying volatile liquids, and to avoid the problems associated with radiation damage to the sample, we have exploited the technology of liquid microjets originally developed by Faubel et al 24 and further developed by Wilson et al [25][26][27][28] Extensive density functional theory calculations were performed with a commercial software package 29 to make spectral assignments and to analyze the effect of pH on the electronic structure of aqueous proline, diglycine, and lysine. To our knowledge, this is the first such study of these systems.…”

Section: Introductionmentioning

confidence: 99%

Local Hydration Environments of Amino Acids and Dipeptides Studied by X-ray Spectroscopy of Liquid Microjets

et al. 2005

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The nitrogen K-edge spectra of aqueous proline and diglycine solutions have been measured by total electron yield near-edge X-ray absorption fine structure (NEXAFS) spectroscopy at neutral and high pH. All observed spectral features have been assigned by comparison to the recently reported spectrum of aqueous glycine and calculated spectra of isolated amino acids and hydrated amino acid clusters. The sharp preedge resonances at 401.3 and 402.6 eV observed in the spectrum of anionic glycine indicate that the nitrogen terminus is in an "acceptor-only" configuration, wherein neither amine proton is involved in hydrogen bonding to the solvent, at high pH. The analogous 1s f σ* NH preedge transitions are absent in the NEXAFS spectrum of anionic proline, implying that the acceptor-only conformation observed in anionic glycine arises from steric shielding induced by free rotation of the amine terminus about the glycine CN bond. Anionic diglycine solutions exhibit a broadened 1s f π* CN resonance at 401.2 eV and a broad shoulder resonance at 403 eV, also suggesting the presence of an acceptor-only species. Although this assignment is not as unambiguous as for glycine, it implies that the nitrogen terminus of most proteins is capable of existing in an acceptor-only conformation at high pH. The NEXAFS spectrum of zwitterionic lysine solution was also measured, exhibiting features similar to those of both anionic and zwitterionic glycine, and leading us to conclude that the R amine group is present in an acceptor-only configuration, while the end of the butylammonium side chain is fully solvated.

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Section: Introductionmentioning

confidence: 99%

Local Hydration Environments of Amino Acids and Dipeptides Studied by X-ray Spectroscopy of Liquid Microjets

et al. 2005

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“…It is noteworthy that the term TIY and ion-detection technique has already been proposed in previous XAS studies of liquid microjets. [17][18][19] Those TIY measurements are however based on the one-electrode detection which is only applicable to windowless liquid samples due to the technique's surface sensitivity. The twoelectrode TIY detection introduced in this study is, on the other hand, applied in liquid cells with membrane windows.…”

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confidence: 99%

“…The incident X-rays exciting a sample actually always create electron -ion pairs upon photoionization, but only the electrons have been generally exploited so far as the charge carrier formulating the TEY detection. The utilization of the corresponding ions is much less explored, [17][18][19] especially for solid sample measurements due to the immobility of the ions.…”

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confidence: 99%

“…This long-distance transport cannot be achieved by electrons because of their extremely short IMFP. The previously reported TIY measurements on liquid microjets [17][18][19] are essentially one-electrode detections which require the electrons or ions produced upon 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 photoionization to escape from the investigated samples into vacuum (sometimes with the assistance of electric bias). Therefore, their probing depth is limited to the length of the electron or ion escape path, similar to the above-discussed TEY detections.…”

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confidence: 99%

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Introducing Ionic-Current Detection for X-ray Absorption Spectroscopy in Liquid Cells

Schön

Xiao

Golnak

et al. 2017

J. Phys. Chem. Lett.

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Photons and electrons are two common relaxation products upon X-ray absorption, enabling fluorescence yield and electron yield detections for X-ray absorption spectroscopy (XAS).The ions that are created during the electron yield process are relaxation products too, which are exploited in this study to produce ion yield for XA detection. The ionic currents measured in a liquid cell filled with water or iron(III) nitrate aqueous solutions exhibit characteristic O K-edge and Fe L-edge absorption profiles as a function of excitation energy. Application of two electrodes installed in the cell is crucial for obtaining the XA spectra of the liquids behind membranes. Using a single electrode can only probe the species adsorbed on the membrane surface. The ionic-current detection, termed as total ion yield (TIY) in this study, also produces an undistorted Fe L-edge XA spectrum, indicating its promising role as a novel detection method for XAS studies in liquid cells.Key words: total ion yield (TIY), ionic current, liquid flow-cell, total electron yield (TEY), X-ray absorption spectroscopy (XAS) TOC GraphicPage 2 of 17 ACS Paragon Plus EnvironmentThe Journal of Physical Chemistry Letters 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 3 Studying the electronic structure of liquid water and aqueous solutions by soft X-rays has attracted much attention in recent years, 1-6 and continues to be a vital research field. Resonant excitation by X-rays is highly element-specific, which makes X-ray absorption spectroscopy (XAS) a widely used tool in many scientific disciplines. Due to the vacuum requirement for soft X-ray propagation, detection of XA spectra for liquid (volatile) samples in vacuum is very challenging. One of the most applied techniques to introduce liquid samples into a vacuum chamber is a liquid flow-cell with an ultra-thin membrane separating the liquid from the vacuum. 7,8 When equipped with multiple electrodes, such a liquid cell can act as a standard electrochemical cell. It is therefore of great interest to combine XAS and the liquid cell technique for in situ/operando investigations on liquid-based materials. [9][10][11][12] When a sample's thickness exceeds the penetration depth of soft X-rays, which is the case for the liquid cell adopted in this study, detection of XA spectra in the transmission mode is not applicable. Therefore, fluorescence yield (FY) or electron yield (EY) must be employed to acquire XA spectra. Due to the significant thickness of typical membranes, e.g. Si 3 N 4 and SiC membranes (~ 100 nm), the electrons created within liquid solutions cannot penetrate the membrane and escape into vacuum. The FY was thus considered the only feasible way to probe the liquid-phase species behind membranes. However, EY has been recently realized in liquid cell studies, thanks to the newly developed graphene membra...

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“…1(a)], this molecule has an aromatic rigid ring structure and occupies its vibrational ground state at the experimental temperature. The NEXAFS experimental data were collected using total electron yield at beamline 8.0.1 at the Advanced Light Source, using prior methods [32] and the ISEELS was previously taken [33]. Peaks 1 and 2 are reproduced well by XCH without vibrations, but with an incorrect peak height ratio.…”

Section: Pacs Numbers: Unknownmentioning

confidence: 99%

Effects of vibrational motion on core-level spectra of prototype organic molecules

Uejio

Schwartz

Saykally

2008

Chemical Physics Letters

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A computational approach is presented for prediction and interpretation of core-level spectra of complex molecules. Applications are presented for several isolated organic molecules, sampling a range of chemical bonding and structural motifs. Comparison with gas phase measurements indicate that spectral lineshapes are accurately reproduced both above and below the ionization potential, without resort to ad hoc broadening. Agreement with experiment is significantly improved upon inclusion of vibrations via molecular dynamics sampling. We isolate and characterize spectral features due to particular electronic transitions enabled by vibrations, noting that even zero-point motion is sufficient in some cases. PACS numbers: UnknownWhen applied to molecular systems, core level spectroscopies are powerful probes of both occupied and unoccupied electronic states, uniquely revealing intimate details of both intra-and inter-molecular interactions [1]. Methods involving x-ray absorption (XAS, NEXAFS, XANES) or x-ray photo-electron spectroscopy (XPS) are increasingly being applied to complex molecular systems, including nucleotides, peptides and large organic molecules [2]. However, a major limitation of this technology is the fact that extraction of molecular information from these experiments often depends explicitly on comparisons with theoretical calculations, which are extremely challenging to perform at experimental accuracy. In this Letter, we describe the extension of a recently developed method for predicting core-level spectra of condensed phases [3] to isolated organic molecules -pyrrole, s-triazine, pyrrolidine and glycine -which demonstrates qualitative improvements over existing methods [4][5][6] in comparison with experiment and provides new insights into the origins of particular spectral features in terms of coupling of electronic and vibrational degrees of freedom.The challenges for simulating gas phase core-level spectra are maintaining accuracy in the following areas: (1) description of the core-hole excited state; (2) representation of both bound excitonic states below the ionization potential (IP) and resonance states in the continuum above the IP; and (3) inclusion of vibrational effects, either due to experiments being performed near room temperature, or from intrinsic zero-point motion.Density functional theory (DFT) [7,8] has proved accurate in reproducing the excitation energies associated with core-level spectra via total energy differences (socalled ∆SCF or ∆KS) [9]. Accordingly, we model the lowest energy core-level excited state self-consistently using a full core-hole and excited electron (XCH) [3]. This is particularly important for molecular systems, where screening of the core-hole excitation is greatly enhanced by the presence of the excited electron, which can be strongly bound to the core-hole in the lowest energy excited state. In contrast, for non-molecular condensed phases, such as covalent and ionic crystalline solids, the inherent dielectric screening of the valence charge density o...

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X-ray Spectroscopy of Liquid Water Microjets

Cited by 158 publications

References 20 publications

Local Hydration Environments of Amino Acids and Dipeptides Studied by X-ray Spectroscopy of Liquid Microjets

Local Hydration Environments of Amino Acids and Dipeptides Studied by X-ray Spectroscopy of Liquid Microjets

Introducing Ionic-Current Detection for X-ray Absorption Spectroscopy in Liquid Cells

Effects of vibrational motion on core-level spectra of prototype organic molecules

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