Production of XeO * in a CW microwave discharge

A low-power CW microwave discharge at 2.45 GHz was used to produce XeO * excimer molecules. It was found that a total gas pressure between 5 and 20 Torr, absorbed power of about 20–100 W, and an oxygen-to-xenon ratio of 1∶100 maximized the XeO( 1 S− 1 D) green emission at 5200 to 5600 Å. The XeO * emission appeared in the cooler parts of the discharge near the containment tube walls and in the electric field nodes of the TM 012 resonant mode.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45480/1/11090_2005_Article_BF01023916.pd

Microscopic simulation of xenon-based optical TPCs in the presence of molecular additives

[EN] We introduce a simulation framework for the transport of high and low energy electrons in xenon-based optical time projection chambers (OTPCs). The simulation relies on elementary cross sections (electron-atom and electron-molecule) and incorporates, in order to compute the gas scintillation, the reaction/quenching rates (atom-atom and atom-molecule) of the first 41 excited states of xenon and the relevant associated excimers, together with their radiative cascade. The results compare positively with observations made in pure xenon and its mixtures with CO2 and CF4 in a range of pressures from 0.1 to 10 bar. This work sheds some light on the elementary processes responsible for the primary and secondary xenon-scintillation mechanisms in the presence of additives, that are of interest to the OTPC technology.DGD is supported by the Ramon y Cajal program (Spain) under contract number RYC-2015-18820. The authors want to acknowledge the RD51 collaboration for encouragement and support during the elaboration of this work, and in particular discussions with F. Resnati, A. Milov, V. Peskov, M. Suzuki and A. F. Borghesani. The NEXT Collaboration acknowledges support from the following agencies and institutions: the European Research Council (ERC) under the Advanced Grant 339787-NEXT; the Ministerio de Economia y Competitividad of Spain under grants FIS2014-53371-C04 and the Severo Ochoa Program SEV-2014-0398; the GVA of Spain under grant PROM-ETEO/2016/120; the Portuguese FCT and FEDER through the program COMPETE, project PTDC/FIS-NUC/2525/2014 and UID/FIS/04559/2013; the U.S. Department of Energy under contracts number DE-AC02-07CH11359 (Fermi National Accelerator Laboratory) and DE-FG02-13ER42020 (Texas A& and the University of Texas at Arlington.Azevedo, C.; Gonzalez-Diaz, D.; Biagi, SF.; Oliveira, CAB.; Henriques, CAO.; Escada, J.; Monrabal, F.... (2018). Microscopic simulation of xenon-based optical TPCs in the presence of molecular additives. Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment. 877:157-172. https://doi.org/10.1016/j.nima.2017.08.049S15717287

Low-power photolytically pumped lasers: Final technical report

We have carried out an extensive series of measurements of the time-resolved Xe/sub 2/* emission spectra following optical pumping by a short-pulse F/sub 2/ laser at 157.6 nm. Most measurements were performed using a gated Optical Multichannel Analyzer detector; we also made measurements using a scanning monochromator fitted with a photomultiplier and using a boxcar integrator for time resolution. The two sets of results agree well and show that both the singlet and triplet emission bands are broader than expected and have center wavelengths closer together than expected. Measurements were performed both at room temperature and at elevated (140/sup 0/C) and reduced (-27/sup 0/C) temperatures. The broad bandwidth of the individual spectral bands was unexpected and conflicted with a previous spectral measurement using optical pumping by the Xe* resonance line from a microwave discharge lamp. Therefore, we also performed a series of spectral measurements using this type of optical pumping. We achieved good agreement with some previous results in the literature, but not with the result in question. We conclude that the present results are reliable. The results presented in this report provide the first definitive measurement of the individual excimer emissions from each of the Xe/sub 2/(0/sub u//sup +/) and Xe/sub 2/(1/sub u/) states. From these measurements and the known ground state potential, we derived a 1/sub u/ potential that reproduces the emission band very well. However, the 1/sub u/ potential is in substantial disagreement with the recent 1/sub u/ potential derived by the Toronto group. 13 refs., 32 figs., 3 tabs

OBSERVATION OF THE C(3/2)←X(1/2)C(3/2)\leftarrow X(1/2) TRANSITION IN XeF

Author Institution: Molecular Physics Laboratory, SRI International$XeF(X_{v}-)$, produced by KrF Laser hotodissociation of $XeF_{2}$, is excited by a doubled dye-laser to $XeF(B_{v^{\prime}})$ and $XeF(C_{v^{\prime}})$ and the broad-band $B\rightarrow A$ and $C\rightarrow A$ fluorescence is detected. The B and C states are distinguished by their differing decay rates at low pressure. Through its fluorescence excitation spectrum the $C\leftarrow X$ transition is observed for the first time. The vibrational analysis of the C-X bands locates the $C(v^{\prime}=0)$ level at $775 cm^{-1}$ below the $B(v^{\prime}=0)$ level, and yields the first experimental vibrational constants for the C state $(\omega_{e} = 346 cm^{-1}$ and $\omega_{e}x_{e} = 2.2 cm^{-1})$. A bandshape analysis of the C-X bands suggests that the equilibrium internuclear separation of the C state lies around 2.45 \AA. Vibrational relaxation and vibrationally resolved collision-induced dissociation of $XeF(X_{v}-)$ are also observed. Supported by the Defense Advanced Research Projects Agency under contract N0014-80-C-0506,through the office of Naval Research

Fullerene-fullerene collisions: fragmentation and electron capture

In this paper, we describe collisions between high-energy (100-keV) fullerene ions (C60+, C602+, C702+, and C703+) and C60. The fast, forward-directed charged collision products are identified, leading to information on electron capture and loss as well as fragmentation. Similar studies are performed on rare-gas targets (He and Xe), and the fragmentation patterns and charge-exchange cross sections are compared and discussed. The electron-capture cross sections are two orders of magnitude larger for collisions with C60 as compared to Xe, while the smaller cluster-ion fragment peaks are only 3-6 times more intense. These observations are discussed in the light of the low ionization energy and the large mass and size of C60

SPECTROSCOPY OF THE TRIATOMIC RARE GAS HALIDES: Rg2XRg_{2}X

$^{1}$ H. H. Nakano, R. M. Hill. D. C. Lorente, D. L. Huestis, M. V. McCusker, and D. J. Eskstrom, SRI Report MP 76-99, December 1976. $^{2}$ D. C. Lorents, R. M. Hill, D. L. Huestis, M. V. McCusker, and H. H. Nakano, Third Summer Colloquium on Electronic Transition Lasers, Snowmass-at-Aspen, Colorado, September 1976. $^{3}$ W. R. Wadt and P. J. Hay, to be published.Author Institution: Molecular Physics Center, Stanford Research InstituteIn the course of a detailed $study^{1}$ of the energy flow kinetics in e-beam excited $Ar/Kr/F_{2}$ mixtures, strong broad emissions were observed in the region of 290 nm and 400 nm. From a characterization of the pressure and temporal behavior of these emission features it was $concluded^{2}$ that the radiating molecules were not the well known ArF (193 nm) or KrF (248 nm) but rather triatomic species $Ar_{2}F$ (290 nm) and $Kr_{2}F$ (400 nm). Recent theoretical $work^{3}$ on $Ar_{2}F$ supports these assignments. We report here a more systematic study of the spectroscopy of the triatomic rare gas fluorides: $Ar_{2}F (290 \pm 25 \ nm), Kr_{2}F (400 \pm 30 \ nm)$, and chlorides $Ar_{2}Cl (246 \pm 14 \ nm), Kr_{2}Cl (325 \pm 15 \ nm)$, and $Xe_{2}Cl (450 \pm 20 nm)$. The wavelength shift from the diatomics is explained in terms of binding in the rare gas molecular ion in the excited state and repulsion between the neutral rare gas atoms in the ground state. These effects are illustrated using potential surfaces for $Ar_{2}F$ calculated by the Diatomics-in-Molecules method

High-flux solar photon processes

This study was commissioned by the National Renewable Energy Laboratory (NREL) for the purpose of identifying high-flux photoprocesses that would lead to beneficial national and commercial applications. The specific focus on high-flux photoprocesses is based on the recent development by NREL of solar concentrator technology capable of delivering record flux levels. We examined photolytic and photocatalytic chemical processes as well as photothermal processes in the search for processes where concentrated solar flux would offer a unique advantage. 37 refs

VISIBLE ABSORPTION BY RARE GAS MOLECULAR IONS AND EXCIMER

$^{1}$H. T. Powell and J. R, Murray, LLL Laser Program Annual Report-1974 (March 1975, unpublished). $^{2}$T. M. Miller, J. H, Ling, R. P, Saxon, and J. T. Moseley, Phys. Rev. A, in press.Author Institution: Molecular Physics Center, Stanford Research InstituteWhile making gain measurements near the 5577 {\AA} $O(^{1}S)$ fluorescence in e-beam excited $Ar/O_{2}$, Powell and $Murray^{1}$ found that during the e-beam pulse the probe laser suffered up to 99.9% absorption. Soon after the termination of the e-beam pulse the absorption disappeared and gain on $Ar O(^{1}S)$ was observed. A similar absorption was observed in e-beam excited argon, krypton, or xenon alone; however, recovery was less rapid. The originally suggested absorber was $Ar_{2}^{+}$. We have $measured^{2}$ the photodissociation cross sections far $Ar_{2}^{+}, Kr_{2}^{+}, and Xe_{2}^{+}$, over the wavelength range 5650 \AA to 6950 \AA, The cross sections at 5650 \AA were $1 \times 10^{-20}, 2 \times 10^{-19}$ and $2 \times 10^{-19}$, respectively. From an investigation of the potential curves for $Ar_{2}^{+}$ it appears clear that the $^{2}\Sigma _{u}^{+} \leftarrow ^{2}{\Pi}_{g}$. transition is at too long a wavelength for the molecular ion to be the absorber discovered by Powell and Murray. We have monitored the temporal and spectral behavior of the absorption in e-beam excited rare gases with and without additives. By comparison with the excimer fluorescence under the same conditions, we have reached the tentative conclusion that the rare gas excimer itself is responsible for the absorption. The probable transition is $^{3}\Sigma_{1u} \leftarrow ^{3}\Pi_{2g}$. Both of these states arise from the $^{3}P_{2}$ levels of the excited rare gas atom