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Gruenwald J, Teodorescu C. Novel target design for a laser-driven aneutronic fusion reactor. FUSION ENGINEERING AND DESIGN 2020. [DOI: 10.1016/j.fusengdes.2019.111397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Fajardo ME. Quantitative Absorption Spectroscopy of Aluminum Atoms in Cryogenic Parahydrogen Solids. J Phys Chem A 2019; 123:10893-10905. [PMID: 31769687 DOI: 10.1021/acs.jpca.9b09318] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We report results of quantitative ultraviolet (UV) and infrared (IR) absorption spectroscopy experiments on Al-atom-doped cryogenic parahydrogen (pH2) solids produced by codeposition of Al vapor and pH2 gas. For Al-atom concentrations [Al] ≲200 parts-per-million (ppm), the Al/pH2 solids are optically transparent and primarily contain isolated Al atoms, with a small admixture of AlH, Al2H2, and Al2H4 molecules formed by UV irradiation and Al-atom recombination/reaction. We assign the Al/pH2 UV absorption spectrum by invoking a large (≈0.6 eV) gas-to-matrix blue shift to accompany the increase in principal quantum number in the 4s 2S ← 3p 2P1/2 transition, as previously discussed for boron-atom-doped pH2 solids. We assign a series of sharp features observed in the 4140-4155 cm-1 IR region to Al-atom-induced Q1(0) and Q1(1) absorptions of the pH2 solid. We use the solid pH2 Q1(0) + S0(0) absorption to determine the sample thickness and to establish a constant pH2 deposition efficiency independent of the flow rate. Using all of these absorption features in concert, we show that the Al-atom flux delivered by the effusive source is well described by the Knudsen-Langmuir equation, calculate an absolute Al-atom deposition yield per mass of aluminum evaporated, and demonstrate both constant Al-atom deposition and isolation efficiencies for [Al] ≲200 ppm. We discuss this unexpected constant Al-atom isolation efficiency in detail and speculate that it indicates nonuniform Al-atom recombination/reaction on the surface of the accreting sample, perhaps dominated by processes occurring near pH2 crystallite grain boundaries. We demonstrate "control" over the deposition process, which we define as the ability to set, achieve, and verify "targets" for the final Al-atom concentrations and pH2 solid thicknesses. This ability is key to sorting out the very different phenomena observed in samples targeting [Al] ≳300 ppm, which are described in the immediately following companion manuscript.
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Affiliation(s)
- Mario E Fajardo
- Munitions Directorate, Ordnance Division, Energetic Materials Branch, AFRL/RWME , Air Force Research Laboratory , 2306 Perimeter Road , Eglin AFB , Florida 32542-5910 , United States
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Wakabayashi T, Momose T, Fajardo ME. Matrix isolation spectroscopy and spectral simulations of isotopically substituted C 60 molecules. J Chem Phys 2019; 151:234301. [PMID: 31864243 DOI: 10.1063/1.5134454] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Isotopically enriched (3.5% 13C) and depleted (0.5% 13C) fullerene C60 molecules are isolated in parahydrogen (pH2) solids at cryogenic temperatures and studied by high resolution (0.01-0.1 cm-1) infrared (IR) absorption measurements. Spectra of natural isotopic abundance (1.1% 13C) C60 molecules isolated in solid pH2, orthodeuterium (oD2), and Ne matrix hosts serve to identify the relatively minor spectral perturbations due to the trapping environments. Spectral features observed for the four IR-active T1u modes of threefold degeneracy in Ih symmetry, namely, T1u(1) at 529.77 cm-1, T1u(2) at 578.24 cm-1, T1u(3) at 1184.7 cm-1, and T1u(4) at 1432 cm-1, are assigned to the superpositions of matrix perturbed vibrational-mode spectra of a number of 13Cn 12C60-n isotopologues. New molecular orbital calculations show the symmetry lowering effects of 13C substitution, namely, split vibrational frequencies and modified IR intensities. IR spectral patterns calculated for the 328 distinct isotopomers of 13Cn 12C60-n up to n = 3 are used to satisfactorily simulate most of the observed absorption features. For the T1u(4) mode at 1432 cm-1, the observed splitting is insensitive to the 13C abundance, indicating spectral perturbations due to Fermi resonance. Weak absorption features at 1545 cm-1 are assigned to a combination of lower frequency modes. We discuss relative and absolute band strengths for the astrophysical application of estimating C60 abundances in planetary nebulae.
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Affiliation(s)
| | - Takamasa Momose
- Department of Chemistry and Department of Physics and Astronomy, The University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - Mario E Fajardo
- Munitions Directorate, US Air Force Research Laboratory AFRL/RWME, Eglin AFB, Florida 32542-5910, USA
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Abstract
We report updated infrared (IR) absorption measurements on vapor-deposited cryogenic parahydrogen (pH2) solids that indicate a ≈10% systematic error in our previous approach for determining a pH2 solid's thickness (S. Tam and M.E. Fajardo. Appl. Spectrosc. 2001. 55(12): 1634-1644). We provide corrected values for the integrated absorption intensities of the Q1(0)+S0(0) and S1(0)+S0(0) bands calculated over the 4495-4520 cm-1 and 4825-4855 cm-1 regions, respectively. New polarized IR absorption spectroscopy data demonstrate the insensitivity to polarization effects of the peak intensity of the QR(0) phonon sideband near 4228 cm-1. This feature provides an even quicker way for determining the thickness of a pH2 solid than via the integrated absorptions.
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Affiliation(s)
- Mario E Fajardo
- Air Force Research Laboratory, Munitions Directorate, Ordnance Division, Energetic Materials Branch, Eglin AFB, USA
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Oliveira AN, Sacramento RL, Moreira LS, Azevedo LOA, Wolff W, Lenz Cesar C. Heteronuclear molecules from matrix isolation sublimation and atomic diffusion. J Chem Phys 2018; 149:084201. [DOI: 10.1063/1.5043421] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- A. N. Oliveira
- INMETRO, Av. Nossa Senhora das Graças, 50, 25250-020 Duque de Caxias, RJ, Brazil
- Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, 21941-972 Rio de Janeiro, RJ, Brazil
| | - R. L. Sacramento
- Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, 21941-972 Rio de Janeiro, RJ, Brazil
| | - L. S. Moreira
- Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, 21941-972 Rio de Janeiro, RJ, Brazil
| | - L. O. A. Azevedo
- Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, 21941-972 Rio de Janeiro, RJ, Brazil
| | - W. Wolff
- Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, 21941-972 Rio de Janeiro, RJ, Brazil
| | - C. Lenz Cesar
- Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, 21941-972 Rio de Janeiro, RJ, Brazil
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Upadhyay S, Kanagin AN, Hartzell C, Christy T, Arnott WP, Momose T, Patterson D, Weinstein JD. Longitudinal Spin Relaxation of Optically Pumped Rubidium Atoms in Solid Parahydrogen. PHYSICAL REVIEW LETTERS 2016; 117:175301. [PMID: 27824470 DOI: 10.1103/physrevlett.117.175301] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Indexed: 06/06/2023]
Abstract
We have grown crystals of solid parahydrogen using a single closed-cycle cryostat. We have doped the crystals with rubidium atoms at densities on the order of 10^{17} cm^{-3} and used optical pumping to polarize the spin state of the implanted atoms. The optical spectrum of the rubidium atoms shows larger broadening than previous work in which the rubidium was implanted in solid argon or neon. However, the optical pumping behavior is significantly improved, with both a larger optical pumping signal and a longer longitudinal relaxation time. The spin relaxation time shows a strong dependence on orthohydrogen impurity levels in the crystal, as well as the applied magnetic field. Current performance is comparable to state-of-the-art solid state systems at comparable spin densities, with potential for improvement at higher parahydrogen purities.
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Affiliation(s)
- Sunil Upadhyay
- Department of Physics, University of Nevada, Reno, Nevada 89557, USA
| | - Andrew N Kanagin
- Department of Physics, University of Nevada, Reno, Nevada 89557, USA
| | - Chase Hartzell
- Department of Physics, University of Nevada, Reno, Nevada 89557, USA
| | - Tim Christy
- Department of Physics, University of Nevada, Reno, Nevada 89557, USA
| | - W Patrick Arnott
- Department of Physics, University of Nevada, Reno, Nevada 89557, USA
| | - Takamasa Momose
- Department of Chemistry, The University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
| | - David Patterson
- Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA
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Sacramento RL, Oliveira AN, Alves BX, Silva BA, Li MS, Wolff W, Cesar CL. Matrix isolation sublimation: An apparatus for producing cryogenic beams of atoms and molecules. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2015; 86:073109. [PMID: 26233358 DOI: 10.1063/1.4926774] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We describe the apparatus to generate cryogenic beams of atoms and molecules based on matrix isolation sublimation. Isolation matrices of Ne and H2 are hosts for atomic and molecular species which are sublimated into vacuum at cryogenic temperatures. The resulting cryogenic beams are used for high-resolution laser spectroscopy. The technique also aims at loading atomic and molecular traps.
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Affiliation(s)
- R L Sacramento
- Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, 21941-972 Rio de Janeiro, RJ, Brazil
| | - A N Oliveira
- Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, 21941-972 Rio de Janeiro, RJ, Brazil
| | - B X Alves
- Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, 21941-972 Rio de Janeiro, RJ, Brazil
| | - B A Silva
- Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, 21941-972 Rio de Janeiro, RJ, Brazil
| | - M S Li
- Instituto de Física de São Carlos, Universidade de São Paulo, Ave. Trabalhador São Carlense, 400, 13565-590 São Carlos, SP, Brazil
| | - W Wolff
- Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, 21941-972 Rio de Janeiro, RJ, Brazil
| | - C L Cesar
- Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, 21941-972 Rio de Janeiro, RJ, Brazil
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Kuma S, Miyamoto Y, Nakajima K, Fukumi A, Kawaguchi K, Nakano I, Sasao N, Tanaka M, Tang J, Taniguchi T, Uetake S, Wakabayashi T, Yoshimi A, Yoshimura M. Coherence decay measurement of v = 2 vibrons in solid parahydrogen. J Chem Phys 2013; 138:024507. [PMID: 23320704 DOI: 10.1063/1.4773893] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The coherence decay of the v = 2 vibrational state (vibrons) of solid parahydrogen was measured via time-resolved coherent anti-Stokes Raman spectroscopy. We found that the decay curve has a non-exponential time profile in the time scale of 200 ns at a low temperature below 5 K and a low orthohydrogen impurity concentration (~0.01%). This behavior, as also observed in the case of the v = 1 vibrons, represents a signature of band structure of the v = 2 state in the solid phase. The maximum coherence decay time of 50 ns in an exponential part was achieved, which shows excellence of the v = 2 state for coherent processes. We also found that finite temperatures, orthohydrogen impurities, and other structural inhomogeneity accelerate the decay, hiding the non-exponential feature of the vibron band.
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Affiliation(s)
- Susumu Kuma
- Research Core for Extreme Quantum World, Okayama University, Okayama 700-8530, Japan.
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Sacramento RL, Alves BX, Almeida DT, Wolff W, Li MS, Cesar CL. Source of slow lithium atoms from Ne or H2matrix isolation sublimation. J Chem Phys 2012; 136:154202. [DOI: 10.1063/1.4704125] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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