Low-energy photoelectron transmission through aerosol overlayers

Amanatidis, Stavros; Yoder, Bruce L.; Signorell, Ruth

doi:10.1063/1.4983995

Cited by 10 publications

(14 citation statements)

References 63 publications

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“…A thymine aerosol of particle size 20–400 nm was generated by nebulization of an aqueous solution of thymine by nitrogen. Afterwards, the particles were dried and introduced into the vacuum of the ionization chamber with the help of an aerodynamic lens system, collimating and guiding the aerosol beam onto a thermodesorber where the particles were vaporized.…”

Section: Methodsmentioning

confidence: 99%

Valence Photoionization of Thymine: Ionization Energies, Vibrational Structure, and Fragmentation Pathways from the Slow to the Ultrafast

Majer

Signorell

Heringa

et al. 2019

Chemistry A European J

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The photoionization of thymine has been studied by using vacuum ultraviolet radiationa nd imaging photoelectronp hotoion coincidences pectroscopy after aerosol flash vaporization andb ulk evaporation.T he two evaporation techniquesh ave been evaluated by comparison of the photoelectrons pectra and breakdown diagrams. The adiabatic ionization energies for the first four electronic states were determined to be 8.922 AE 0.008,9 .851 AE 0.008, 10.30 AE 0.02, and 10.82 AE 0.01 eV.V ibrational features have been assigned for the first three electronic states with the help of Franck-Condon factor calculations based on densityf unctional theory and wave function theory vibrational analysis within the harmonic approximation. The breakdown diagram of thymine, as supported by composite methoda bi nitio cal-culations,s uggestst hat the main fragment ions are formed in sequential HNCO-, CO-, and H-loss dissociation steps from the thymine parenti on, with the first step corresponding to ar etro-Diels-Alder reaction. The dissociation rate constants were extractedf rom the photoion time-of-flight distributions and used together with the breakdown curvest oc onstruct as tatistical model to determine 0K appearance energies of 11.15 AE 0.16 and 11.95 AE 0.09 eV for the m/z 83 and 55 fragment ions, respectively.T hese results have allowedu st o revise previously proposed fragmentation mechanismsa nd to proposeamodel for the final, nonstatistical H-losss tep in the breakdown diagram, yielding the m/z 54 fragment ion at an appearance energy of 13.24 eV.

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Section: Methodsmentioning

confidence: 99%

Valence Photoionization of Thymine: Ionization Energies, Vibrational Structure, and Fragmentation Pathways from the Slow to the Ultrafast

Majer

Signorell

Heringa

et al. 2019

Chemistry A European J

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“…For details see refs. [18,29,34]. The Monte Carlo model for electron scattering described in section S4 and the recommended liquid CSs described in section S5 are used for the scattering calculations.…”

Section: Calculated Vmismentioning

confidence: 99%

Electron Scattering in Liquid Water and Amorphous Ice: A Striking Resemblance

Signorell

2020

Phys. Rev. Lett.

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The lack of accurate low-energy electron scattering cross sections for liquid water is a substantial source of uncertainty in the modelling of radiation chemistry and biology. The use of existing amorphous ice scattering cross sections for lack of liquid data has been discussed controversially over decades. Here, we compare experimental photoemission data of liquid water with corresponding predictions using amorphous ice cross sections, with the aim of resolving the debate regarding the difference of electron scattering in liquid water and amorphous ice. We find very similar scattering properties in the liquid and the ice for electron kinetic energies up to a few hundred electron volts. The scattering cross sections recommended here for liquid water are an extension of the amorphous ice cross sections. Within the framework of currently available experimental data, our work answers one of the most debated questions regarding electron scattering in liquid water.

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“…An overflow outlet at the nebulizer was used to keep the inlet system at ambient pressure. The aerosol was sampled through an aerodynamic lens with a 200 μm critical orifice at a flow rate of approximately 6 cm 3 s −1 . The aerodynamic lens focuses particles in the 20–400 nm size range into a collimated particle beam perpendicular to the VUV radiation axis and directs them at the heated conical copper tip of the in‐house built thermodesorber, shown in Figure .…”

Section: Experimental and Computational Methodsmentioning

confidence: 99%

“…The aerosol was sampled through an aerodynamic lens with a2 00 mmc ritical orifice at af low rate of approximately 6cm 3 s À1 . [48][49][50][51][52] The aerodynamic lens focuses particles in the 20-400 nm size range into acollimated particle beam perpendicular to the VUV radiation axis and directs them at the heated conical copper tip of the in-house built thermodesorber,s hown in Figure 1. The position of the temperature controlled heated finger with 3mmd iameter and ac oncave, conically shaped tip is adjustable in all three directions using micrometer screws and was optimized for ion signal intensity.U pon impact, the heating effect of the finger is slightly enhanced by the kinetic energy of the aerosol particles to evaporate the particles in high vacuum, creating ag as phase plume in the immediate vicinity of the ionization region.…”

Section: Aerosolsampling Setupmentioning

confidence: 99%

The Distant Double Bond Determines the Fate of the Carboxylic Group in the Dissociative Photoionization of Oleic Acid

et al. 2017

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The valence threshold photoionization of oleic acid has been studied using synchrotron VUV radiation and imaging photoelectron photoion coincidence (iPEPICO) spectroscopy. An oleic acid aerosol beam was impacted on a copper thermodesorber, heated to 130 °C, to evaporate the particles quantitatively. Upon threshold photoionization, oleic acid produces the intact parent ion first, followed by dehydration at higher energies. Starting at ca. 10 eV, a large number of fragment ions slowly rise suggesting several fragmentation coordinates with quasi-degenerate activation energies. However, water loss is the dominant low-energy dissociation channel, and it is shown to be closely related to the unsaturated carbon chain. In the lowest-barrier process, one of the four allylic hydrogen atoms is transferred to the carboxyl group to form the leaving water molecule and a cyclic ketone fragment ion. A statistical model to analyze the breakdown diagram and measured rate constants yields a 0 K appearance energy of 9.77 eV, which can be compared with the density functional theory result of 9.19 eV. Alternative H-transfer steps yielding a terminal C=O group are ruled out based on energetics and kinetics arguments. Some of the previous photoionization mass spectrometric studies also reported 2 amu and 26 amu loss fragment ions, corresponding to hydrogen and acetylene loss. We could not identify such peaks in the mass spectrum of oleic acid.

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Low-energy photoelectron transmission through aerosol overlayers

Cited by 10 publications

References 63 publications

Valence Photoionization of Thymine: Ionization Energies, Vibrational Structure, and Fragmentation Pathways from the Slow to the Ultrafast

Valence Photoionization of Thymine: Ionization Energies, Vibrational Structure, and Fragmentation Pathways from the Slow to the Ultrafast

Electron Scattering in Liquid Water and Amorphous Ice: A Striking Resemblance

The Distant Double Bond Determines the Fate of the Carboxylic Group in the Dissociative Photoionization of Oleic Acid

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