NASA LAW abstract

[Gillian Nave <gnave@nist.gov>]

I have attached my registration form and abstract for the NASA laboratory 
astrophysics workshop. Please let me know if there is any problem with the 
preparation of the abstract. I shall send the fee with the printed 
registration form by regular mail.

Gillian Nave

-------------------------------------------------------
Gillian Nave

Atomic Physics Division,
National Institute of Standards and Technology, stop 8422
100 Bureau Drive,
Gaithersburg,
MD 20899-8422

Tel: 301-975 4311
Fax: 301-975 3038
email: gnave@nist.gov


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\begin{document}

\title{Atomic Oscillator Strengths in the Vacuum Ultraviolet
}

\author{Gillian~Nave, Craig~J.~Sansonetti and Csilla~I.~Szabo \\ 
National Institute of Standards and Technology,\\
Gaithersburg, MD}

\date{\today}

\maketitle

\begin{abstract}

Transitions in singly-ionized and doubly-ionized iron-group elements
give rise to prominent emission lines from a wide variety of
astrophysical objects. Some of the most important lines are formed
when the upper energy level is excited by radiation from hydrogen at
1216~\AA (Ly-$\alpha$), giving strong fluorescence lines from the
vacuum ultraviolet to the infrared. These emission lines are important
diagnostics of astrophysical plasmas, but laboratory oscillator
strengths are unavailable.

The established way to measure accurate oscillator strengths for
atomic lines combines the measurement of a lifetime of an upper energy
level with a separate measurement of the branching fractions of all
the lines emitted from that level. This technique relies on being able
to observe {\em all} the spectral lines emitted by the upper level,
which range down to Ly-$\alpha$ or below for many fluorescence
lines. Methods of measuring branching fractions using Fourier
transform spectroscopy are limited to wavelengths above about
1400~\AA\ and cannot observe all the spectral lines required. 

We have developed techniques to measure branching fractions in the
vacuum ultraviolet using our 10.7~m normal incidence grating
spectrograph. For this we use phosphor image plates as replacements
for the photographic plates previously used on this instrument. Image
plates are sensitive to wavelengths from the X-ray region to 2200~\AA,
and have a linear intensity response with a dynamic range of at least
10~$^4$. We have recorded spectra of iron-neon hollow cathode and
Penning discharges, using a deuterium standard lamp for radiometric
calibration. Our measurements of Fe II branching ratios around
1600~\AA\ agree with previously-published measurements to within 8~\%.
The reproducibility of our D$_2$ standard lamp spectra at shorter
wavelengths is 4~\% , enabling us to measure branching ratios down to
1150~\AA. We are also investigating methods of radiometric calibration
below 1150~\AA\ using hollow cathode standard lamps.
This will enable us to measure branching ratios down to
800~\AA\ or below -- a region with many resonance lines of
doubly-ionized spectra and critical for the analysis of data from the
Far Ultraviolet Spectroscopic Explorer.

This work is partially funded by NASA under the inter-agency agreement W-10,255.
\end{abstract}

\end{document}

Registration form
-------------------------------------------------------------------------------
Last name:        Nave
First name:       Gillian		
Middle name/initial:
Affiliation:      National Institute of Standards and Technology
Street Address:   100 Bureau Drive
City:             Gaithersburg
State:            MD
Postal Code:      20899-8422
Country:          U.S.A.
Tel:              301-975 4311
Fax:              301-975 3038
E mail:           gnave@nist.gov
Citizenship*:     United Kingdom  
Abstract title    Atomic Oscillator Strengths in the Vacuum Ultraviolet
Special requirements:
*Non-US citizens should contact Cara Loomis if travel reimbursement for 
 the Workshop is required.