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Similar a Comprehensive wavelengths and energy levels of Fe II, Cr II and other iron-group elements using Fourier transform and grating spectroscopy (20)
Comprehensive wavelengths and energy levels of Fe II, Cr II and other iron-group elements using Fourier transform and grating spectroscopy
1. Comprehensive wavelengths and energy levels of Fe II, Cr
II and other iron-group elements using Fourier transform
and grating spectroscopy
PI: Gillian Nave
Co I: Craig J. Sansonet
National Institute of Standards and Technology,
Gaithersburg, MD
NASA inter-agency agreement NNH10AN38I.
Start Date: January 2010.
End Date: December 2012.
2. Objectives
1)Prepare a comprehensive linelist of about 15 000 lines in Fe II. Wavelengths from 90
nm to 5.5 µm. Wavelength uncertainty around 1:107
. Identify lines using about 1000
energy levels with uncertainties of around 0.002 cm-1
.
2)Prepare similar linelist for Cr II, containing over 4000 lines from 700 levels.
3)Record and analyze spectra of additional iron-group element, selected by
consultation with astronomical community.
Research this year has focused on finishing Fe II and the UV/visible spectrum of Cr II.
3. High-resolution UV spectra from the
Hubble Space Telescope
J. C. Brandt et al., AsJ 117, 1505 (1999)
Data for synthetic spectra require
accurate wavelengths and oscillator
strengths with comprehensive coverage
for all elements and ionization stages
present in the stellar spectrum.
4. Background to objectives: Fe II
●
Last major analysis of Fe II in 1978. Contained 3272 lines from 576 levels:
S. Johansson, “The spectrum and term system of Fe II,” Phys. Scr. 18, 217 (1978).
●
FT spectra of Fe-Ne and Fe-Ar hollow cathode lamps analyzed by G. Nave: Precise
wavelengths in Fe I published: 1991 and 1992.
●
Collaboration with S. Johansson (Lund Univ., Sweden) begun in 1992 – combined FTS
& grating spectra contain 34000 lines from 83 nm to 5.5 µm.
●
9500 of these lines are Fe I:
G. Nave, S. Johansson, R. C. M. Learner, A. P. Thorne, J. W. Brault, “A new multplet
table for Fe I,” ApJS, 94, 221 (1994).
●
About 15000 are Fe II. Analysis begun by S. Johansson, but remained uncompleted
when Johansson died in 2008.
8. High-excitation levels from HR6000
•
109 new levels from 3d6
(3
L)4f (L=P, H, F, G) found using UVSE
spectra of HR600 & 46 Aql Castelli & Kurucz (A&A 520, A57
(2010))
•
Majority of lines too high excitation to give lines in laboratory
spectra, but some lines from these levels in lab
•
Currently verifying which of the lines from these levels in lab
spectra are correct.
•
Calculations of Kurucz helpful, but not predictive.
•
Are all levels correct?
10. Current status of Fe II
•
Identifications for 13500 spectral lines in Fe II confirmed.
About 500 have more than one identification.
•
Verifying levels of Kurucz & Castelli – roughly 100 more lines.
•
Need to add (5
D)5g-6h lines (about 60 lines).
•
Revise intensity scale?
•
Aim to finish by end of 2011.
12. Background to research: Cr II
●
Last major analysis of Cr II in 1951. Contained 1843 lines from 99 levels:
●
C. C. Kiess, “Descripton and analysis of the second spectrum of chromium, Cr II,” J. Res.
NBS 47, 385.
●
ASD contains 743 levels, most of variable quality, unpublished with no published lines.
●
Spectra of low-current Pt-Cr-Ne lamps taken at NIST for calibration of STIS using FTS and
grating:
C. J. Sansonet, F. Kerber, J. Reader, M R. Rosa, “Characterizaton of the far-ultraviolet
spectrum of Pt/Cr-Ne hollow cathode lamps as used on the space telescope imaging
spectrograph on board the Hubble space telescope,” ApJ 153, 555 (2004).
These are the spectra being used in the current analysis. Will be combined with IR spectra
of high-current hollow cathode lamp recorded using NIST 2-m FTS.
13. 2-m FTS
High Current HCL
2.0 A
2.0 Torr Ne
Si photodiode
FT700 VUV FTS
Low Current HCL
20 mA
≈ 5.0 Torr Ne
R106UH PMT
UG11 Filter
FT700 VUV FTS
Low Current HCL
20 mA
≈ 5.0 Torr Ne
R1220 PMT
14. Current Status of Cr II Project
●
Grating spectra recorded in region 1131 – 1844 Å
928 Cr II lines
●
FTS spectra and measured in region 1568 – 4000 Å
2750 Cr II lines
●
FTS spectra recorded from 3000 – 11000 Å.
●
Energy levels optimization
3457 total classified lines
3361 used in level optimization
284 of 334 even levels optimized
347 of 369 odd levels optimized
15. Many level values change far
outside the estimated 0.05 cm-1
uncertainty of the levels from
Sugar & Corliss
61% of optimized levels
have uncertainties
<0.005 cm-1
. 91% have
uncertainties <0.02 cm-1
16. •
Chromium is more abundant in chemically peculiar stars than the sun.
•
Ritz wavelength of the Cr II line 4848 Å agrees poorly with astronomical
spectra. There is no precise laboratory wavelength for this line.
•
From our optimized levels the Cr II 4848 Å line wavelength is
4848.2506(5) Å, an increase of 0.0156 Å from the original Ritz value.
Ryabchikova, unpublished
17. Future directions.
● Fe II to be finished by end of 2011.
● Cr II vis/UV finished soon, IR region to be measured and
analyzed.
● Plan to start another singly-ionized element next year: Mn II?
18. 1994 2010
Lab (full time) 3 1
Lab (part time) 0 1/4
Data compilations (full time) 2 3
Data compilations
(part time)
3 4
NIST atomic spectroscopy group
Then and now
19. Other astronomy projects in NIST Atomic Spectroscopy
Group
● Calibration of Pt/Ne hollow cathode lamps for GHRS (NASA-
funded).
● Calibration of Pt/Cr/Ne hcls for STIS (NASA funded).
● Aging tests of Pt lamps for COS (NASA funded).
● Calibration of Th/Ar lamps in infrared (ESO/NASA funded) for
CRIRES.
● Calibration of U/Ne lamps in IR (NRC postdoctoral project).
NASA funding essential to continuation of laboratory
program in NIST Atomic Spectroscopy Group.
