Ruby spectra R1, R2 lines

The ruby fluorescence pressure scale is an optical method to measure pressure within a sample chamber of a diamond anvil cell apparatus.[1] Since it is an optical method, which fully make use of the transparency of diamond anvils and only requires an access to a small scale laser generator, it has become the most prevalent pressure gauge method in high pressure sciences.

Principles

Ruby is chromium-doped corundum (Al2O3). The Cr3+ in corundum's lattice forms an octahedra with surrounding oxygen ions. The octahedral crystal field together with spin-orbital interaction results in different energy levels. Once 3d electrons in Cr3+ are energized by lasers, the excited electrons would go to 4T2 and 2T2 levels. Later they return to 2E levels and the R1, R2 lines come from luminescence from 2E levels to 4A2 ground level.[2] The energy difference of 2E levels are 29 cm−1, corresponding to the splitting of R1, R2 lines at 1.39 nm.[2]

Development

Ruby fluorescence spectra has two strong sharp lines, R1 and R2. R1 refers to the stronger intensity and lower energy (longer wavelength) excitation and is used to gauge pressure.

Pressure is calculated as: , where λ0 is the R1 wavelength measured measured at 1atm, a and b are constants. (e.g. a = 19.04, b = 5[3])

Since first demonstrated by Forman and colleagues in 1972,[4][5] many scientists have contributed to the establishment of accurate ruby pressure scale in various experimental conditions.

A likely incomplete summary of is given below:

Year First Author a b Primary pressure standard used Temperature Pressure range Pressure transmitting medium References
1972 R. A. Forman - -, linear Transitions of CCl4, H2O, C2H5Br, n-C7H16 Room temperature 2.2 GPa See standards used [4]
1978 H. K. Mao 1904 5 Ag, Cu, Mo, Pd Room temperature 6 - 100 GPa M-E, H2O [3]
1986 H. K. Mao 1904 7.665 Cu, Ag, Ar Room temperature 80 GPa Ar [6]
2004 A. Dewaele 1904 9.5 Al, Cu, W Room temperature 153 GPa Helium [7]
2005 A. D. Chijioke 1876(6.7) 10.71(0.14) Au, Pt Room temperature 150 GPa Helium, Hydrogen, Ar [8]
2008 S.D Jacobsen 1904 10.32(7) MgO Room temperature 118 GPa Helium [9]
2012 H. Yamaoka 1762*ln(λ/λ0) Ruby R1 Low temperature to 16K 26 GPa M-E, Silicone oil [10]
2020 G. Shen 1870 5.63(3) MgO, Mo, Cu, Diamond Room temperature 150 GPa Helium [11]

References

  1. ↑ Bassett, William A. (2009-05-21). "Diamond anvil cell, 50th birthday". High Pressure Research. 29 (2): 163–186. doi:10.1080/08957950802597239. ISSN 0895-7959. S2CID 15204168.
  2. 1 2 Syassen, K. (June 2008). "Ruby under pressure". High Pressure Research. 28 (2): 75–126. doi:10.1080/08957950802235640. ISSN 0895-7959. S2CID 95275637.
  3. 1 2 Mao, H. K.; Bell, P. M.; Shaner, J. W.; Steinberg, D. J. (June 1978). "Specific volume measurements of Cu, Mo, Pd, and Ag and calibration of the ruby "R1" fluorescence pressure gauge from 0.06 to 1 Mbar". Journal of Applied Physics. 49 (6): 3276–3283. doi:10.1063/1.325277. ISSN 0021-8979.
  4. 1 2 Forman, Richard A.; Piermarini, Gasper J.; Barnett, J. Dean; Block, Stanley (1972-04-21). "Pressure Measurement Made by the Utilization of Ruby Sharp-Line Luminescence". Science. 176 (4032): 284–285. doi:10.1126/science.176.4032.284. ISSN 0036-8075. PMID 17791916. S2CID 8845394.
  5. ↑ Piermarini, G.J. (Nov 2011). "High pressure X-ray crystallography with the diamond cell at NIST/NBS". Journal of Research of the National Institute of Standards and Technology. 106 (6): 910–912. doi:10.6028/jres.106.045. ISSN 1044-677X. PMC 4865304. PMID 27500054. S2CID 18150811.
  6. ↑ Mao, H. K.; Xu, J.; Bell, P. M. (1986). "Calibration of the ruby pressure gauge to 800 kbar under quasi-hydrostatic conditions". Journal of Geophysical Research. 91 (B5): 4673. doi:10.1029/jb091ib05p04673. ISSN 0148-0227.
  7. ↑ Dewaele, Agnès; Loubeyre, Paul; Mezouar, Mohamed (2004-09-22). "Equations of state of six metals above94GPa". Physical Review B. 70 (9). doi:10.1103/physrevb.70.094112. ISSN 1098-0121.
  8. ↑ Chijioke, Akobuije D.; Nellis, W. J.; Soldatov, A.; Silvera, Isaac F. (Dec 2005). "The ruby pressure standard to 150GPa". Journal of Applied Physics. 98 (11): 114905. doi:10.1063/1.2135877. ISSN 0021-8979.
  9. ↑ Jacobsen, S. D.; Holl, C. M.; Adams, K. A.; Fischer, R. A.; Martin, E. S.; Bina, C. R.; Lin, J.-F.; Prakapenka, V. B.; Kubo, A.; Dera, P. (2008-11-01). "Compression of single-crystal magnesium oxide to 118 GPa and a ruby pressure gauge for helium pressure media". American Mineralogist. 93 (11–12): 1823–1828. doi:10.2138/am.2008.2988. ISSN 0003-004X. S2CID 21661728.
  10. ↑ Yamaoka, Hitoshi; Zekko, Yumiko; Jarrige, Ignace; Lin, Jung-Fu; Hiraoka, Nozomu; Ishii, Hirofumi; Tsuei, Ku-Ding; Mizuki, Jun'ichiro (2012-12-15). "Ruby pressure scale in a low-temperature diamond anvil cell". Journal of Applied Physics. 112 (12): 124503. doi:10.1063/1.4769305. ISSN 0021-8979.
  11. ↑ Shen, Guoyin; Wang, Yanbin; Dewaele, Agnes; Wu, Christine; Fratanduono, Dayne E.; Eggert, Jon; Klotz, Stefan; Dziubek, Kamil F.; Loubeyre, Paul; Fat’yanov, Oleg V.; Asimow, Paul D. (2020-07-02). "Toward an international practical pressure scale: A proposal for an IPPS ruby gauge (IPPS-Ruby2020)". High Pressure Research. 40 (3): 299–314. doi:10.1080/08957959.2020.1791107. ISSN 0895-7959. S2CID 225460396.
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