VI/150 Recombination coefficients for O II lines - SSB2 (Storey+, 2017)
Recombination coefficients for O II lines in nebular conditions.
Storey P.J., Sochi T., Bastin R.
<Mon. Not. R. Astron. Soc., 470, 379-389>
=2017MNRAS.470..379S 2017MNRAS.470..379S
=2017yCat.6150....0S 2017yCat.6150....0S
ADC_Keywords: Atomic physics
Keywords: atomic data - atomic processes - radiation mechanisms -
planetary nebulae - H II regions - astrochemistry - plasmas -
numerical methods - oxygen - recombination lines -
emission coefficients - recombination coefficients
Abstract:
We present the results of a calculation of recombination
coefficientscients for O^2 + +e-^ using an intermediate coupling
treatment that fully accounts for the dependence of the distribution
of population among the ground levels of O2+ on electron density and
temperature. The calculation is extended down to low electron
temperatures where dielectronic recombination arising from Rydberg
states converging on the O2+ ground levels is an important process.
The data, which consist of emission coefficientscients for 8889
recombination lines and recombination coefficientscients for the
ground and metastable states of O+ are in Cases A, B and C, and are
organised as a function of the electron temperature and number
density, as well as wavelength. An interactive fortran 77 data server
is also provided as an accessory for mining the line emission
coefficients and obtaining Lagrange interpolated values for any
choice of the two variables between the explicitly provided values for
any set of wavelengths. Some illustrations of the application of the
new data to nebular observations are also provided.
Description:
The list presents emission and recombination coefficients of the O II
transitions arising from recombination of doubly-ionised oxygen O2+
with a free electron. An intermediate coupling treatment that fully
accounts for the dependence of the distribution of population among
the ground levels of O2+ on electron temperature (Te) and electron
number density (Ne) is used. The calculation is extended down to low
electron temperatures where dielectronic recombination arising from
Rydberg states converging on the O2+ ground levels is an important
process. The data are given as function of Te and Ne in three
Cases (A, B and C). The data are suitable in particular for the
physical conditions found in planetary nebulae and HII regions. An
interactive data server in the form of fortran 77 code is also
provided as an accessory for mining the data of emission coefficients
and obtaining Lagrange interpolated values for any choice of the two
variables, Te and Ne, between the explicitly provided values for
any set of wavelengths and for any Case.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 30 3 List of repertories
DataFiles/* . 2 Files for OII data
DataServer/* . 1 fortran 77 code
Examples/* . 4 Examples
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See also:
VI/141 : Computed List of Collision Strengths for nebular [OIII] Optical
and Infrared Lines - SSB (Storey+, 2014)
VI/144 : Computed List of Effective Collision Strengths for nebular [OIII] -
SS3 (Storey+, 2015)
Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Rep Repertory name
13- 30 A18 --- Content Content of the directory
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Description of the data files (DataFiles/*):
The data are contained in 2 files that we describe in the following
bullet points:
1. Data file named "OIIlines_ABC": this file consists of two main
sections preceded by a short header which consists of a general
description of the file structure and the abbreviations used to
label and explain the data blocks and their units. The structure
of these sections is as follows:
a. The first section consists of 8889 indexed text lines corresponding
to the provided 8889 OII transitions where each text line contains
full identification of the corresponding transition by its upper
and lower level as well as its wavelength and other relevant atomic
designations.
b. The second section consists of 8889 parts where each part
corresponds to one transition as indexed above. Each part is made
of three blocks where each block corresponds to one of the three
Cases. Each one of these blocks is a rectangular array of emission
coefficients of the indexed transition arranged in 25 rows, as a
function of log10(Te) between 2.0-4.4 in steps of 0.1, and 16
columns as a function of log10(Ne) between 2.0-5.0 in steps of
0.2.
2. Data file named "OIImeta_ABC": this file contains the recombination
coefficients to the ground and meta-stable levels of O+ as
functions of Te and Ne and Case (A, B and C). The file contains
14 data blocks which are described in the following:
a. A block for the effective recombination coefficients of the ground
level 2s2 2p3 4So3/2 in Case A.
b. Four blocks for the effective recombination coefficients of the two
levels 2s2 2p3 2Do5/2 and 2Do3/2 each in Case A and B.
c. Six blocks for the effective recombination coefficients of the two
levels 2s2 2p3 2Po3/2 and 2Po1/2 each in
Case A, B and C.
d. Three blocks for the total recombination coefficients, one block
for each Case.
Each one of the 14 data blocks is structured as a function of Te and
Ne in log10 identical to the structure of the emission coefficient
blocks in the "OIIlines_ABC" file, as described above.
Note: the units of the provided data are as follows:
(a) Te: K
(b) Ne: cm-3
(c) Emission coefficients: erg.cm^3/s per O2+ ion per electron
(d) Recombination coefficients: cm^3/s per O2+ ion per electron
(e) Wavelengths: Angstroem
Description of the data server (DataServer/*):
The data server is a fortran 77 code named "exlines.f" designed to
excavate the emission coefficient data in the "OIIlines_ABC" file in
interactive mode by offering branching selections for the user. The
size of the recombination coefficient data in the "OIImeta_ABC" file
is very small. Moreover, the main intended use of these data is in
modelling and hence there is no compelling need for interpolation.
Therefore, no accessory for mining and interpolating these data was
provided.
The data server reads the "OIIlines_ABC" file and provides easy access
to the lines and their emission coefficients at the desired Te and
Ne values for a given selection of wavelength and Case. When the
required data are within the above-stated Te and Ne ranges but are
not at the grid points of Te and Ne as described above, a 6-point
Lagrange interpolation in Te and Ne is used to provide the desired
data.
There are two main options offered by the data server: generating a
line list and extracting emission coefficients for a user supplied
list of lines in user specified conditions. These options are
explained in the following bullet points:
(1) Generating a line list where the server offers two choices:
(1a) Listing all the 8889 lines.
(1b) Specifying a wavelength range for the list of lines desired by
the user.
In each one of these choices, two files are generated that contain the
list of lines where the lines in one of these files (named
"OIIdatalisteorder") are ordered in decreasing order of emission
coefficient and in the other file (named "OIIdatalistworder") in
increasing order of wavelength. The full list in the latter file is
preceded by a list of only the strongest lines in the required
wavelength range. The emission coefficients in these files correspond
to typical nebular conditions of Te=10000 and Ne=10000.
(2) Extracting emission coefficients where the user is asked to supply
a list of lines in a text file (OIIdata_xxxx) for which the data
are required. The user then has the choice between:
(2a) Providing a list of Te-Ne pairs in a file (TDpairs_xxxx) for
which the data are needed. The first entry in the file
TDpairs_xxxx is the number of pairs followed by the pairs each
in a row.
(2b) Providing a range of log10(Te) and log10(Ne) in a file
(TDranges_xxxx) defining a one- or two-dimensional grid for
which the data are required. The file TDranges_xxxx contains 3 rows.
The first row contains the number of T_e and N_e points. The
second row contains the first value of log10(Te) in the grid
followed by the step size. The third row is the same as the second
row with regard to log10(Ne).
In all of these 4 choices (i.e. 1a, 1b, 2a and 2b) the user has the
option to have the data for Case A, B or C. The distributed data
bundle contains 4 examples (one for each choice) with the input and
output data files as well as the screen output to demonstrate the use
of the data server.
Acknowledgements:
P.J. Storey: University College London, pjs(at)star.ucl.ac.uk
Taha Sochi: University College London, t.sochi(at)ucl.ac.uk
Robert Bastin: Surbiton High School
(End) Taha Sochi [University College London], Patricia Vannier [CDS] 11-May-2017