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Revisiting Iridium Optical Constants for the Chandra HRMA Effective Area

Review and update of Ir optical constants for Chandra Calibration Workshop 2004. Detailed analysis of reflected IRIDIUM, CHROMIUM, ZERODUR layers using synchrotron reflectance measurements. Comparison with Henke/Gullikson results.

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Revisiting Iridium Optical Constants for the Chandra HRMA Effective Area

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  1. Revisiting Iridium Optical Constants for the Chandra HRMA Effective Area DE Graessle, D Jerius, R Soufli, AJ Nelson, EM Gullikson Chandra Calibration Workshop 2004

  2. Participants in the Chandra Synchrotron Calibration Program …include, but not necessarily limited to the following: T. H. Burbine, G. Chartas, A.M. Clark, J.P. Cobuzzi, J.J. Fitch, R. Francoeur, B. Harris, R.H. Ingram, J.Z. Juda, E.M. Kellogg, A.G. Roy, D.A. Schwartz, E.S. Sullivan, J.B. Sweeney, and P. Zhao. Beamline scientists and technicians such as M. Sagurton (X8A), R. Alkire (X8C), S. Mrowka and Andreas Stonas (ALS 6.3.2) also contributed advice and assistance when needed. The authors are grateful for discussions and encouragement provided by the late L.P. Van Speybroeck, whom we remember fondly. Chandra Calibration Workshop 2004

  3. Outline • Introduction • Modeling and parameters • Review: Optical Constants 5-12 keV • Overlayer modeling at M-edges • 1000-2000 eV optical constants • Low-energy results • XPS measurements of the overlayer Chandra Calibration Workshop 2004

  4. Review and update of the Ir optical constants is timely. • Currently we use 940-12000eV results from a single mirror. • Mirror-to-mirror M-edge discrepancies were not resolved as of launch date. • Assumed n X CH2 overlayer, unverified. • 50-1000 eV low-energy data never reduced for use in Chandra calibration. • Indications of Ir M-edge artifacts in Chandra source analyses. Chandra Calibration Workshop 2004

  5. Reviewing the coating configuration: Chandra Calibration Workshop 2004

  6. Optical constants were determined from synchrotron reflectance measurements versus angle and versus energy. • R vs q to determine Ir, Cr layer depths, surface roughness/interdiffusion depths, and overlayer. • R vs E to determine Ir d(E), b(E), with layer and roughness parameters frozen. • Four beamlines used, with energy ranges broken down for optimized monochromaticity and intensity. • At least one angle scan per energy range for alignment/parameters, except below 1000 eV. Chandra Calibration Workshop 2004

  7. Reflected Ray Incident Beam Overlayer, if used Transmitted Ray IRIDIUM CHROMIUM ZERODUR We employ a four-layer model with an optional overlayer to derive d, b. Chandra Calibration Workshop 2004

  8. 5-12 keV optical constants: A1 mirrors are indistiguishable. Chandra Calibration Workshop 2004

  9. In the Ir M-edge region, an overlayer is necessary for fits, consistency. d(E) Overlayer used No overlayer used b(E) Chandra Calibration Workshop 2004

  10. M-edges require an overlayer in model due to masking of Ir absorption. d(E) M33p3/2 Overlayer used M43d3/2 No overlayer M53d5/2 b(E) Chandra Calibration Workshop 2004

  11. 1000-2000 eV b(E) is also more consistent with overlayer. d(E) b(E) Chandra Calibration Workshop 2004

  12. Low-energy data: As with M-edges, the detail obtained is significant. d(E) N64f5/2 N74f7/2 O35p3/2 b(E) Chandra Calibration Workshop 2004

  13. Some significant differences appear from tabulated between N-edges. d(E) b(E) Chandra Calibration Workshop 2004

  14. C- and O-K leave signatures with our naïve overlayer composition. b(E) d(E) C-K N-K O-K N34p3/2 Chandra Calibration Workshop 2004

  15. In the featureless 600-1200 eV range, we obtain only slight variations from tabulated. d(E) b(E) Chandra Calibration Workshop 2004

  16. Here are our current best results (not yet implemented in the CalDB) Chandra Calibration Workshop 2004

  17. Our current results, with 1995 Henke/Gullikson for comparison. Chandra Calibration Workshop 2004

  18. 5 CHANDRA1367A1.spe x 10 6 1367-A1 -Ir4f5 area 1 5 -Ir4f7 -Ir4d5 4 -Ir4d3 -Ir4p3 -O1s 3 c/s -Ir4p1 -N1s -Ir4s -O KLL -C1s 2 -Si2s 1 0 1100 1000 900 800 700 600 500 400 300 200 100 0 Binding Energy (eV) XPS survey scan of 065 reveals several components in overlayer. Chandra Calibration Workshop 2004

  19. 4 CHANDRA1367A2.spe x 10 2.5 C1s CHANDRA 065 2 1.5 c/s 1 CHANDRA 127 0.5 0 292 290 288 286 284 282 280 278 Binding Energy (eV) High-resolution C1s Spectra Chandra Calibration Workshop 2004

  20. CHANDRA1367A2.spe 12000 O1s 10000 CHANDRA 065 8000 c/s 6000 4000 2000 CHANDRA 127 0 546 544 542 540 538 536 534 532 530 528 526 524 Binding Energy (eV) High-resolution O1s Spectra Chandra Calibration Workshop 2004

  21. CHANDRA1367A2.spe N1s 3000 CHANDRA 065 2500 2000 c/s 1500 CHANDRA 127 1000 500 0 412 410 408 406 404 402 400 398 396 394 392 Binding Energy (eV) High-resolution N1s Spectra Chandra Calibration Workshop 2004

  22. CHANDRA1367A2.spe 3500 3000 2500 Si2s CHANDRA 065 2000 c/s 1500 1000 CHANDRA 127 500 0 166 164 162 160 158 156 154 152 150 148 146 144 Binding Energy (eV) High-resolution Si2s Spectra Chandra Calibration Workshop 2004

  23. 4 CHANDRA1367A2.spe x 10 16 Ir4f7/2 Ir4f5/2 14 12 CHANDRA 065 10 c/s 8 6 4 2 CHANDRA 127 0 78 76 74 72 70 68 66 64 62 60 58 56 Binding Energy (eV) High-resolution Ir4f Spectra Chandra Calibration Workshop 2004

  24. Summary • We have a nearly final set of Ir optical constants, which will soon be finalized and published. => Appl. Optics; Gullikson tables. • Refinements must be folded into HRMA model to evaluate Ir M-edge artifacts in Chandra analyses. (See D Jerius, this workshop.) • XPS confirms the overlayer, and may be evalutated further to help mitigate C, O, and N signatures in low-energy results. Chandra Calibration Workshop 2004

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