Characterization of Regolith And Trace Economic Resources (CRATER): An Orbitrap-based laser desorption mass spectrometry instrument for in situ exploration of the Moon.

Rationale: Characterization of Regolith And Trace Economic Resources (CRATER), an Orbitrap™-based laser desorption mass spectrometry instrument designed to conduct high-precision, spatially resolved analyses of planetary materials, is capable of answering outstanding science questions about the Moon's formation and the subsequent processes that have modified its (sub)surface.

Methods: Here, we describe the baseline design of the CRATER flight model, which requires <20 000 cm  volume, <10 kg mass, and <60 W peak power. The analytical capabilities and performance metrics of a prototype that meets the full functionality of the flight model are demonstrated.

Linear Ion Trap Mass Spectrometer (LITMS) Instrument Field and Laboratory Tests as Part of the ARADS Field Campaigns.

The highly compact Linear Ion Trap Mass Spectrometer (LITMS), developed at NASA Goddard Space Flight Center, combines Mars-ambient laser desorption-mass spectrometry (LD-MS) and pyrolysis-gas chromatography-mass spectrometry (GC-MS) through a single, miniaturized linear ion trap mass analyzer. The LITMS instrument is based on the Mars Organic Molecule Analyser (MOMA) investigation developed for the European Space Agency's ExoMars Rover Mission with further enhanced analytical features such as dual polarity ion detection and a dual frequency RF (radio frequency) power supply allowing for an increased mass range. The LITMS brassboard prototype underwent an extensive repackaging effort to produce a highly compact system for terrestrial field testing, allowing for molecular sample analysis in rugged planetary analog environments outside the laboratory.

Metabolic Processes Preserved as Biosignatures in Iron-Oxidizing Microorganisms: Implications for Biosignature Detection on Mars.

Iron-oxidizing bacteria occupy a distinct environmental niche. These chemolithoautotrophic organisms require very little oxygen (when neutrophilic) or outcompete oxygen for access to Fe(II) (when acidophilic). The utilization of Fe(II) as an electron donor makes them strong analog organisms for any potential life that could be found on Mars.

Mars Organic Molecule Analyzer (MOMA) laser desorption/ionization source design and performance characterization.

The Mars Organic Molecule Analyzer (MOMA), a dual-source, ion trap-based instrument capable of both pyrolysis-gas chromatography mass spectrometry (pyr/GC-MS) and laser desorption/ionization mass spectrometry (LDI-MS), is the core astrobiology investigation on the ExoMars rover. The MOMA instrument will be the first spaceflight mass analyzer to exploit the LDI technique to detect refractory organic compounds and characterize host mineralogy; this mode of analysis will be conducted at Mars ambient conditions. In order to achieve high performance in the Martian environment while keeping the instrument compact and low power, a number of innovative designs and components have been implemented for MOMA.

The Mars Organic Molecule Analyzer (MOMA) Instrument: Characterization of Organic Material in Martian Sediments.

The Mars Organic Molecule Analyzer (MOMA) instrument onboard the ESA/Roscosmos ExoMars rover (to launch in July, 2020) will analyze volatile and refractory organic compounds in martian surface and subsurface sediments. In this study, we describe the design, current status of development, and analytical capabilities of the instrument. Data acquired on preliminary MOMA flight-like hardware and experimental setups are also presented, illustrating their contribution to the overall science return of the mission.

Aluminum Zintl anion moieties within sodium aluminum clusters.

Through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations, we have established that aluminum moieties within selected sodium-aluminum clusters are Zintl anions. Sodium-aluminum cluster anions, Na(m)Al(n)(-), were generated in a pulsed arc discharge source. After mass selection, their photoelectron spectra were measured by a magnetic bottle, electron energy analyzer.

Multiphoton photoelectron emission microscopy of single Au nanorods: combined experimental and theoretical study of rod morphology and dielectric environment on localized surface plasmon resonances.

Multiphoton photoelectron emission from individual Au nanorods deposited on indium tin oxide (ITO) substrates is studied via scanning photoionization microscopy, based on femtosecond laser excitation at frequencies near the rod longitudinal surface plasmon resonance (LSPR). The observed resonances in photoemission correlate strongly with plasmon resonances measured in dark field microscopy (DFM), thus establishing a novel scheme for wavelength-resolved study of plasmons in isolated metallic nanoparticles based on highly sensitive electron counting methods. In this work, we explore experimental and theoretical effects of (i) morphology and (ii) aspect ratio (AR) for longitudinal plasmon resonance behavior in Au nanorods.

Coherent multiphoton photoelectron emission from single au nanorods: the critical role of plasmonic electric near-field enhancement.

Electron emission from individual Au nanorods deposited on indium-tin-oxide (ITO) following excitation with femtosecond laser pulses near the rod longitudinal plasmon resonance is studied via scanning photoionization microscopy. The measured electron signal is observed to strongly depend on the excitation laser polarization and wavelength. Correlated secondary electron microscopy (SEM) and dark-field microscopy (DFM) studies of the same nanorods unambiguously confirm that maximum electron emission results from (i) laser polarization aligned with the rod long axis and (ii) laser wavelength resonant with the localized surface plasmon resonance.

Plasmonic near-electric field enhancement effects in ultrafast photoelectron emission: correlated spatial and laser polarization microscopy studies of individual Ag nanocubes.

Electron emission from single, supported Ag nanocubes excited with ultrafast laser pulses (λ = 800 nm) is studied via spatial and polarization correlated (i) dark field scattering microscopy (DFM), (ii) scanning photoionization microscopy (SPIM), and (iii) high-resolution transmission electron microscopy (HRTEM). Laser-induced electron emission is found to peak for laser polarization aligned with cube diagonals, suggesting the critical influence of plasmonic near-field enhancement of the incident electric field on the overall electron yield. For laser pulses with photon energy below the metal work function, coherent multiphoton photoelectron emission (MPPE) is identified as the most probable mechanism responsible for electron emission from Ag nanocubes and likely metal nanoparticles/surfaces in general.

Photoelectron spectroscopic and computational studies of the Pt@Pb₁₀⁻¹ and Pt@Pb₁₂¹⁻/²⁻ anions.

A combination of anion photoelectron spectroscopy and density functional theory calculations has elucidated the geometric and electronic structure of gas-phase endohedral Pt/Pb cage cluster anions. The anions, Pt@Pb₁₀⁻¹ and Pt@Pb₁₂¹⁻ were prepared from "preassembled" clusters generated from crystalline samples of [K(2,2,2-crypt)]₂[Pt@Pb₁₂] that were brought into the gas phase using a unique infrared desorption/photoemission anion source. The use of crystalline [K(2,2,2-crypt)]₂[Pt@Pb₁₂] also provided access to K[Pt@Pb(n)](-) anions in the gas phase (i.

Polarization-dependent scanning photoionization microscopy: ultrafast plasmon-mediated electron ejection dynamics in single Au nanorods.

This work investigates plasmon-enhanced multiphoton scanning photoelectron emission microscopy (SPIM) of single gold nanorods under vacuum conditions. Striking differences in their photoemission properties are observed for nanorods deposited either on 2 nm thick Pt films or 10 nm thick indium tin oxide (ITO) films. On a Pt support, the Au nanorods display fourth-order photoionization when excited at 800 nm, a wavelength corresponding to their plasmon resonance in aqueous solution.

Electronic structure and properties of isoelectronic magic clusters: Al13X (X=H,Au,Li,Na,K,Rb,Cs).

The equilibrium structure, stability, and electronic properties of the Al(13)X (X=H,Au,Li,Na,K,Rb,Cs) clusters have been studied using a combination of photoelectron spectroscopy experiment and density functional theory. All these clusters constitute 40 electron systems with 39 electrons contributed by the 13 Al atoms and 1 electron contributed by each of the X (X=H,Au,Li,Na,K,Rb,Cs) atom. A systematic study allows us to investigate whether all electrons contributed by the X atoms are alike and whether the structure, stability, and properties of all the magic clusters are similar.

Communications: Chain and double-ring polymeric structures: Observation of Al(n)H(3n+1) (-) (n=4-8) and Al(4)H(14) (-).

A pulsed arc discharge source was used to prepare gas-phase, aluminum hydride cluster anions, Al(n)H(m) (-), exhibiting enhanced hydrogen content. The maximum number of hydrogen atoms in Al(n)H(m) (-) species was m=3n+1 for n=5-8, i.e.

Reactivity of aluminum cluster anions with ammonia: selective etching of Al11(-) and Al12(-).

Reactivity of aluminum cluster anions toward ammonia was studied via mass spectrometry. Highly selective etching of Al(11)(-) and Al(12)(-) was observed at low concentrations of ammonia. However, at sufficiently high concentrations of ammonia, all other sizes of aluminum cluster anions, except for Al(13)(-), were also observed to deplete.

Photoelectron spectroscopy of lanthanide-silicon cluster anions LnSi(n)(-) (3

Photoelectron spectroscopy was utilized to study a variety of LnSi(n)(-) cluster anions (Ln = Yb, Eu, Sm, Gd, Ho, Pr; 3 View Article and Find Full Text PDF

Heteroborane analogs of silicon clusters: experimental and theoretical studies on Bi2Si5 and Bi2Si5(-).

We have investigated the electronic structure of anionic and neutral Bi(2)Si(5) by means of anion photoelectron spectroscopy and density functional calculations. Both the experiments and calculations reveal that the Bi(2)Si(5)(-) anion prefers to adopt a distorted trigonal-bipyramidal structure with Bi(2) bridges. Following the isolobal analogy between divalent Si and B-H group, we show that both neutral Bi(2)Si(5) and neutral Bi(2)B(5)H(5) adopt similar pentagonal-bipyrmidal geometries and have analogous orbital energy patterns.

Photoelectron spectroscopy of europium-silicon cluster anions, EuSin- (3

We report the photoelectron spectra of EuSi(n) (-) cluster anions (3 View Article and Find Full Text PDF

Photoelectron spectroscopy of the parent anions of the nucleotides, adenosine-5'-monophosphate and 2'deoxyadenosine-5'-monophosphate.

The parent anions of the nucleotides, adenosine-5(')-monophosphate (AMPH) and 2(')deoxyadenosine-5(')-monophosphate (dAMPH) were generated in a novel source and their photoelectron spectra recorded with 3.49 eV photons. Vertical detachment energy (VDE) and the adiabatic electron affinity (EA(a)) values were extracted from each of the two spectra.

Intrinsic electrophilic properties of nucleosides: photoelectron spectroscopy of their parent anions.

The nucleoside parent anions 2(')-deoxythymidine(-), 2(')-deoxycytidine(-), 2(')-deoxyadenosine(-), uridine(-), cytidine(-), adenosine(-), and guanosine(-) were generated in a novel source, employing a combination of infrared desorption, electron photoemission, and a gas jet expansion. Once mass selected, the anion photoelectron spectrum of each of these was recorded. In the three cases in which comparisons were possible, the vertical detachment energies and likely adiabatic electron affinities extracted from these spectra agreed well with the values calculated both by Richardson et al.

Ground state structures and photoelectron spectroscopy of [Com(coronene)]- complexes.

A synergistic approach involving theory and experiment has been used to study the structure and properties of neutral and negatively charged cobalt-coronene [Com(coronene)] complexes. The calculations are based on density functional theory with generalized gradient approximation for exchange and correlation potential, while the experiments are carried out using photoelectron spectroscopy of mass selected anions. The authors show that the geometries of neutral and anionic Co(coronene) and Co2(coronene) are different from those of the corresponding iron-coronene complexes and that both the Co atom and the dimer prefer to occupy eta2-bridge binding sites.