S. M. Angel

The synthesis and photophysical characterization of nanometer-size ZnS with and without Mn2+ are reported. Without Mn2+, the ZnS nanoclusters emit in the blue upon ultraviolet excitation. ZnS doped with 1−5% Mn2+ (presumably in Zn2+ sites) yields the orange emission observed for bulk Zn:Mn phosphors but with greatly reduced emissive lifetimes. ZnS with surface-bound Mn2+, in contrast, emits in the ultraviolet with even shorter lifetimes. Thus, the physical location of Mn2+ in the ZnS nanocluster determines its optical properties.

Abstract The SuperCam instrument suite provides the Mars 2020 rover, Perseverance, with a number of versatile remote-sensing techniques that can be used at long distance as well as within the robotic-arm workspace. These include laser-induced breakdown spectroscopy (LIBS), remote time-resolved Raman and luminescence spectroscopies, and visible and infrared (VISIR; separately referred to as VIS and IR) reflectance spectroscopy. A remote micro-imager (RMI) provides high-resolution color context imaging, and a microphone can be used as a stand-alone tool for environmental studies or to determine physical properties of rocks and soils from shock waves of laser-produced plasmas. SuperCam is built in three parts: The mast unit (MU), consisting of the laser, telescope, RMI, IR spectrometer, and associated electronics, is described in a companion paper. The on-board calibration targets are described in another companion paper. Here we describe SuperCam’s body unit (BU) and testing of the integrated instrument. The BU, mounted inside the rover body, receives light from the MU via a 5.8 m optical fiber. The light is split into three wavelength bands by a demultiplexer, and is routed via fiber bundles to three optical spectrometers, two of which (UV and violet; 245–340 and 385–465 nm) are crossed Czerny-Turner reflection spectrometers, nearly identical to their counterparts on ChemCam. The third is a high-efficiency transmission spectrometer containing an optical intensifier capable of gating exposures to 100 ns or longer, with variable delay times relative to the laser pulse. This spectrometer covers 535–853 nm ( $105\text{--}7070~\text{cm}^{-1}$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mn>105</mml:mn> <mml:mtext>–</mml:mtext> <mml:mn>7070</mml:mn> <mml:mspace/> <mml:msup> <mml:mtext>cm</mml:mtext> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:math> Raman shift relative to the 532 nm green laser beam) with $12~\text{cm}^{-1}$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mn>12</mml:mn> <mml:mspace/> <mml:msup> <mml:mtext>cm</mml:mtext> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:math> full-width at half-maximum peak resolution in the Raman fingerprint region. The BU electronics boards interface with the rover and control the instrument, returning data to the rover. Thermal systems maintain a warm temperature during cruise to Mars to avoid contamination on the optics, and cool the detectors during operations on Mars. Results obtained with the integrated instrument demonstrate its capabilities for LIBS, for which a library of 332 standards was developed. Examples of Raman and VISIR spectroscopy are shown, demonstrating clear mineral identification with both techniques. Luminescence spectra demonstrate the utility of having both spectral and temporal dimensions. Finally, RMI and microphone tests on the rover demonstrate the capabilities of these subsystems as well.

We have designed and demonstrated a standoff Raman system for detecting high explosive materials at distances up to 50 meters in ambient light conditions. In the system, light is collected using an 8-in. Schmidt-Cassegrain telescope fiber-coupled to an f/1.8 spectrograph with a gated intensified charge-coupled device (ICCD) detector. A frequency-doubled Nd : YAG (532 nm) pulsed (10 Hz) laser is used as the excitation source for measuring remote spectra of samples containing up to 8% explosive materials. The explosives RDX, TNT, and PETN as well as nitrate- and chlorate-containing materials were used to evaluate the performance of the system with samples placed at distances of 27 and 50 meters. Laser power studies were performed to determine the effects of laser heating and photodegradation on the samples. Raman signal levels were found to increase linearly with increasing laser energy up to approximately 3 x 10(6) W/cm2 for all samples except TNT, which showed some evidence of photo- or thermal degradation at higher laser power densities. Detector gate width studies showed that Raman spectra could be acquired in high levels of ambient light using a 10 microsecond gate width.

ADVERTISEMENT RETURN TO ISSUEPREVFEATURENEXTEmission Enhancement Mechanisms in Dual-Pulse LIBSJon Scaffidi, S. Michael Angel, and David A. CremersCite this: Anal. Chem. 2006, 78, 1, 24–32Publication Date (Web):January 1, 2006Publication History Published online1 January 2006Published inissue 1 January 2006https://pubs.acs.org/doi/10.1021/ac069342zhttps://doi.org/10.1021/ac069342znewsACS Publications. This publication is available under these Terms of Use. Request reuse permissions This publication is free to access through this site. Learn MoreArticle Views2656Altmetric-Citations172LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail PDF (474 KB) Get e-Alertsclose Get e-Alerts

In this paper we report the first observations of dual-pulse laser-induced breakdown spectroscopy (LIBS) signal enhancements by using a pre-ablation spark. In this technique a laser pulse is brought in parallel to the sample surface and focused a few millimeters above it to form an air plasma or air spark. A few microseconds later a second laser pulse, which is focused on the sample, ablates sample material and forms the LIBS plasma from which analyte emission occurs. In this way, large LIBS signal enhancements, 11-to 33-fold, are observed for copper and lead, respectively, relative to the signal in the absence of the air spark. In all cases where enhanced LIBS signals are seen, greatly enhanced sample ablation also occurs.