We determined Raman cross-sections of various organic liquids and inorganic polyatomic ions in aqueous solutions with a 532 nm pulsed laser using remote Raman systems developed at the University of Hawaii. Using a calibrated integrating sphere as a light source, we converted the intensity counts in the spectrum of the light from the integrating sphere measured with UH remote Raman instrument to spectral radiance. From these data, a response function of the remote Raman instrument was obtained. With the intensity-calibrated instrument, we collected remote Raman data from a standard 1 mm path length fused silica spectrophotometer cell filled with cyclohexane. The measured value of the differential Raman cross-section for the 801 cm(-1) vibrational mode of cyclohexane is 4.55 x 10(-30) cm(2) sr(-1) molecule(-1) when excited by a 532 nm laser, in good agreement with the values reported in the literature. Using the measured cyclohexane Raman cross-section as a reference and relative Raman mode intensities of the various ions and organic liquids, we calculated the Raman cross-sections of the strongest Raman lines of nitrate, sulfate, carbonate, phosphate ions, and organic liquids by maintaining same experimental conditions for remote Raman detection. These relative Raman cross-section values will be useful for estimating detection capabilities of remote Raman systems for planetary exploration.

A S canning St andoff R aman S pectroscopy (SSTRS) system has been developed to map out the spatial distributions of selected minerals at long distances (10–100 m). The SSTRS is based on a standoff Raman system, which is mounted inside a custom pan and tilt scanner. Computer software is used to control the direction of the pan-tilt scanner and to point the laser beam onto the distant samples. Measurements are made in an x-y grid pattern on a target area defined by the user. The Raman spectra collected at each grid point are processed to identify the distribution of minerals present from their respective Raman fingerprints. In the initial experiment, the Raman spectra of barite (BaSO 4 ), gypsum (CaSO 4 ·2H 2 O), plagioclase feldspar (solid solution of NaAlSi 3 O 8 -CaAl 2 Si 2 O 8 ), α -quartz ( α -SiO 2 ) rocks, and silica glass were measured at 30 m distance. The Raman spectra at the grid points are measured and processed to obtain a Raman mineral image of the distant minerals by selecting respective Raman fingerprints of α -quartz, gypsum and plagioclase feldspar. The ability to provide interpolated Raman images of distant mineral species is illustrated. The new SSTRS system works well and now offers the ability to obtain spatial distribution maps of distant mineral species from their Raman fingerprints.

The capability to analyze and detect the composition of distant samples (minerals, organics, and chemicals) in real time is of interest for various fields including detecting explosives, geological surveying, and pollution mapping. For the past 10 years, the University of Hawaii has been developing standoff Raman systems suitable for measuring Raman spectra of various chemicals in daytime or nighttime. In this article we present standoff Raman spectra of various minerals and chemicals obtained from a distance of 120 m using single laser pulse excitation during daytime. The standoff Raman system utilizes an 8-inch Meade telescope as collection optics and a frequency-doubled 532 nm Nd : YAG laser with pulse energy of 100 mJ/pulse and pulse width of 10 us. A gated intensified charge-coupled device (ICCD) detector is used to measure time-resolved Raman spectra in daytime with detection time of 100 ns. A gate delay of 800 us (equivalent to target placed at 120 m distance) was used to minimize interference from the atmospheric gases along the laser beam path and near-field scattering. Reproducible, good quality single. shot Raman spectra of various inorganic and organic chemicals and minerals such as ammonium nitrate, potassium perchlorate, sulfur, gypsum, calcite, benzene, nitrobenzene, etc., were obtained through sealed glass vials during daytime. The data indicate that various chemicals could easily be identified from their Raman fingerprint spectra from a far standoff distance in real time using single-shot laser excitation.

The University of Hawaii has been developing portable remote Raman systems capable of detecting chemicals in daylight from a safe standoff distance. We present data on standoff detection of chemicals used in the synthesis of homemade explosives (HME) using a portable standoff Raman system utilizing an 8-inch telescope. Data show that good-quality Raman spectra of various hazardous chemicals such as ammonium nitrate, potassium nitrate, potassium perchlorate, sulfur, nitrobenzene, benzene, acetone, various organic and inorganic chemicals etc. could be easily obtained from remote distances, tested up to 120 meters, with a single-pulse laser excitation and with detection time less than 1 μs. The system uses a frequency-doubled Nd:YAG pulsed laser source (532 nm, 100 mJ/pulse, 15 Hz, pulse width 10 ns) capable of firing a single or double pulse. The double-pulse configuration also allows the system to perform standoff LIBS (Laser-Induced Breakdown Spectroscopy) at 50 m range. In the standoff Raman detection, the doublepulse sequence simply doubles the signal to noise ratio. Significant improvement in the quality of Raman spectra is observed when the standoff detection is made with 1s integration time. The system uses a 50-micron slit and has spectral resolution of 8 cm-1. The HME chemicals could be easily detected through clear and brown glass bottles, PP and HDPE plastic bottles, and also through fluorescent plastic water bottles. Standoff Raman detection of HME chemical from a 10 m distance through non-visible concealed bottles in plastic bubble wrap packaging is demonstrated with 1 s integration time. Possible applications of the standoff Raman system for homeland security and environmental monitoring are discussed.

A scanning standoff Raman spectroscopy system has been developed to measure the molecular species of distant samples in two dimensions. Computer software is used to control the scanner pan and tilt angles, and Raman measurements are collected of the distant sample area in an xy grid pattern. The Raman spectra at each grid point are measured and processed to obtain an image of the distant surface composition. The ability to provide interpolated images of distant molecular species is illustrated. Copyright (c) 2011 John Wiley & Sons, Ltd.

Surface-enhanced Raman scattering (SERS) utilizing colloidal silver and gold has been demonstrated to provide a rapid means of measuring the Raman spectra of microorganisms in the fingerprint region. In this study, we have introduced microcavity substrates coated with alternating layers of silver and gold thin films for measuring the Raman spectra of four strains of E. coli. These microcavitiy substrates have been prepared by placing glass microspheres between two polished aluminum substrates and pressing them together using a standard lab press. After removing the glass microspheres from the substrates, the substrates have been coated with 15 to 70 nm thick films of chromium, silver and gold in a precise order. The cavities were evaluated for SERS enhancement by measuring Raman spectra of dilute rhodamine 6G (R6G) down to 10(-8) M. With these microcavities, we have investigated the SERS spectra of four chemically competent strains of E. coli (One Shot OmniMAX 2-T1, Mach1-T1, Stbl3, and TOP10). Replicate SERS spectra of all the four e-coli strains show excellent reproducibility. Visual examination of the spectra, however, reveals differences in the spectra of these strains. To confirm this observation, we have used multivariate analysis for positive identification and discrimination between the strains.

At the University of Hawaii, we have developed a compact, portable remote Raman and Laser-Induced Breakdown Spectroscopy (LIBS) system with a 532 nm pulsed laser for planetary exploration under the Mars Instrument Development Program. The compact time-resolved remote Raman and LIBS system consists of (i) a regular 85 mm Nikon (F/1.8) camera lens with clear aperture of 50 mm as collection optics, (ii) a miniature spectrograph that occupies 1/14th the volume of a comparable commercial spectrograph from Kaiser Optical Systems Inc., (iii) a custom mini-ICCD detector, and (iv) a small frequency-doubled 532 nm Nd:YAG pulsed laser (30 mJ/pulse, 20 Hz) with a 10x beam expander. In the standoff Raman mode the system is capable of measuring various minerals, water, ices, and atmospheric gases from a 50 meter range with a 10 s integration time. At shorter distances of 10 m or less, good quality Raman spectra can be obtained within 1 s. The time-gated system is capable of detecting both the target mineral as well as the atmospheric gases before the target using their Raman fingerprints. Various materials can easily be identified through glass, plastic, and water media. The time-gating capability makes the system insensitive to window material, which is highly desirable for future missions to Venus where instruments are expected to be within the lander. The standoff LIBS range is 10 m and LIBS spectra of various minerals can be obtained with single laser pulse excitation. The standoff LIBS capability provides additional elemental verification of the targeted material.

Introduction: Spectral data from orbit indicate that phyllosilicates are widespread on Mars, including smectites (with a range of compositions from aluminous to Fe,Mg-rich), kaolin group minerals, chlorites, serpentine, and illite/muscovite [1, 2, 3]. This broad range of detected phyllosilicates indicates a variety of formation conditions and hence the importance of phyllosilicate mineralogy in petrogenetic interpretations for Mars. Many phyllosilicate-depositing systems, especially those associated with lower-temperature aqueous systems, are likely targets for study of potential habitable environments on Mars; all four candidate sites for the 2011 Mars Science Laboratory (MSL) contain claymineral associations of primary interest in this regard [4]. Our goal in this study was to evaluate the operation of Laser Induced Breakdown Spectroscopy (LIBS), as carried on the ChemCam instrument for MSL, against a range of phyllosilicates to define operational parameters and possibilities for characterization. LIBS involves generating a plasma by focusing a high power laser onto the sample surface. The plasma contains electronically excited atoms, ions and small molecules that emit light as they relax to lower electronic states. This emission is collected and used to quantitatively determine the elemental composition and sample identification. Samples: Clay powder samples used in these experiments were NIST chemical standard 97b and Clay Minerals Society (CMS) source clays KGa-2, PFl-1, SHCa1, STx-1b and SWy-2. Table 1 contains XRD determinations of mineralogy for these 6 clay samples. Rock powder samples from the Brammer catalog of standards were also selected as chemical reference materials. The geologic standards were basalts (BCR2, BHVO-2, BIR-1, GBW 07105, GUWBM, MO-14), dolomites (JDo-1, GBW 07217a), andesites (JA-1, JA-

The authors have utilized a recently developed compact Raman spectrometer equipped with an 85mm focal length (f/1.8) Nikon camera lens and a custom mini-ICCD detector at the University of Hawaii for measuring remote Raman spectra of minerals under supercritical CO2 (Venus chamber, ∼102atm pressure and 423K) excited with a pulsed 532nm laser beam of 6mJ/pulse and 10Hz. These experiments demonstrate that by focusing a frequency-doubled 532nm Nd:YAG pulsed laser beam with a 10× beam expander to a 1mm spot on minerals located at 2m inside a Venus chamber, it is possible to measure the remote Raman spectra of anhydrous sulfates, carbonates, and silicate minerals relevant to Venus exploration during daytime or nighttime with 10s integration time. The remote Raman spectra of gypsum, anhydrite, barite, dolomite and siderite contain fingerprint Raman lines along with the Fermi resonance doublet of CO2. Raman spectra of gypsum revealed dehydration of the mineral with time under supercritical CO2 at 423K. Fingerprint Raman lines of olivine, diopside, wollastonite and α-quartz can easily be identified in the spectra of these respective minerals under supercritical CO2. The results of the present study show that time-resolved remote Raman spectroscopy with a compact Raman spectrometer of moderate resolution equipped with a gated intensified CCD detector and low power laser source could be a potential tool for exploring Venus surface mineralogy both during daytime and nighttime from a lander.

The control of sodium in CIGS solar cells is critical to achieve high efficiency devices, but to date composition measurement techniques either cannot detect the sub-one atomic percent levels (for example, x-ray fluorescence (XRF)) or are expensive, time consuming, and destructive (examples include SIMS, XPS/ESCA). We employed an inexpensive, fast, and minimally destructive method to measure the concentration of sodium in CIGS solar cells fabricated at the Hawaii Natural Energy Institute (HNEI). Laser induced breakdown spectroscopy (LIBS) was used to determine the relative concentration of sodium. Two different analysis methods of the LIBS data were explored: the first assumes local thermal equilibrium (LTE) of the plasma and is calibration-free while the second employs comparison of relative peak heights after calibration to determine the concentration. Analysis is presented for solar cells produced on thin titanium foils where sodium fluoride is included in the deposition process to incorporate sodium into the CIGS layer.

We present data on standoff detection of chemicals used in synthesis of homemade explosives (HME) using a compact portable standoff Raman system developed at the University of Hawaii. Data presented in this article show that good quality Raman spectra of various organic and inorganic chemicals, including hazardous chemicals such as ammonium nitrate, potassium nitrate, potassium perchlorate, sulfur, nitrobenzene, benzene, acetone, and gasoline, can be easily obtained from remote distances with a compact standoff Raman system utilizing only a regular 85 mm Nikon camera lens as collection optics. Raman spectra of various chemicals showing clear Raman fingerprints obtained from targets placed at 50 m distance in daylight with 1 to 10 second of integration time are presented in this article. A frequency-doubled mini Nd:YAG pulsed laser source (532 nm, 30 mJ/pulse, 20 Hz, pulse width 8 ns) is used in an oblique geometry to excite the target located at 50 m distance. The standoff Raman system uses a compact spectrograph of size 10 cm (length) x 8.2 cm (width) x 5.2 cm (height) with spectral coverage from 100 to 4500 cm(-1) Stokes-Raman shifted from 532 nm laser excitation and is equipped with a gated thermo-electrically cooled ICCD detector. The system is capable of detecting both the target as well as the atmospheric gases before the target. Various chemicals could be easily identified through glass, plastic, and water media. Possible applications of the standoff Raman system for homeland security and environmental monitoring are discussed.

A Monte Carlo radiative transfer program (Atmosphere–Ocean 3-Dimensional, AO3D) for modeling the coupled atmosphere–ocean environment has been developed. The code allows for the specification of optical properties for the atmosphere, land and ocean. Light rays are tracked as they pass between the atmosphere and the ocean, reflect off the ocean surface, the ocean floor, and off land, or are absorbed. In this version the polarization of light rays is not considered. The optical properties of each horizontally homogeneous layer within the atmosphere and ocean can be set on a layer-by-layer basis with a choice of phase functions, absorption and scattering coefficients, and index of refraction. A wind-dependent Cox and Munk ocean surface realization (with whitecaps) is implemented to model refraction and reflection from surface waves. Either spherical- or flat-Earth models can be used, and all refraction and reflection are accounted for. The AO3D model has been tested by parts, and as a whole by comparison with single- and total-scattering calculations from other radiative transfer codes. Comparisons with Monte Carlo calculations by Adams and Kattawar (agreement in TOA radiance within the published precision ∼2%), MODTRAN4 (agreement in spherical-shell atmosphere (SSA) sky radiance within about 2%) and Coupled DIScrete Ordinate Radiative Transfer (COART) (agreement in plane-parallel (PP) sky radiance within 2%) are shown. Sun photometer measurements (including large air mass values) at the Mauna Loa Observatory are compared to AO3D simulations (for a spherical Earth) and suggest that a thin aerosol layer was present above the observatory at the time of the measurements.