Optical Properties of Graphite and Absorption and Scattering
Cross Sections for Graphite Grains
The data provided here are from the paper
"Graphite Revisited" (Draine 2016, ApJ accepted).
Please cite that paper if you use these data.
The data are of two type:
- complex dielectric functions for graphite (both E || c and E perp c).
- complex dielectric function estimated for turbostratic graphite.
- cross sections for absorption and scattering for grains composed of
graphite, including results for spheres and selected spheroids.
Dielectric functions
Draine (2016) presents a new estimate for the
dielectric tensor of graphite, from submm to X-ray energies.
The files below present dielectric functions, and cross sections
for spherical and spheroidal grains calculated using these
dielectric functions:
Cross sections for single-crystal graphite spheres
Draine (2016) has carried out accurate DDA calculations
(using DDSCAT 7.3.1),
with full treatment of the anisotropic dielectric tensor of graphite,
for absorption and scattering by randomly-oriented single-crystal
graphite spheres, for wavelengths from 0.1um to 10um.
The results in these files were obtained by extrapolation to N=infinity
from DDSCAT calculations with N_1=59278 and N_2=140408 dipoles.
Results are given for selected values of aeff = radius of sphere.
Cross sections for single-crystal graphite spheroids
Draine (2016) has carried out accurate DDA calculations
(using DDSCAT 7.3.1), with full treatment of the anisotropic dielectric
tensor of graphite,
for absorption and scattering by randomly-oriented graphite oblate spheroids
(b/a=1.4; c axis parallel to the spheroid symmetry axis) for selected sizes, for wavelengths from 0.1um to 10um.
The rsults in these files were obtained by extrapolation to N=infinity
from DDSCAT calculations with N_1=60476 and N_2=131040 dipoles.
Results are given for selected values of aeff = radius of equal-volume sphere.
Cross sections for turbostratic graphite spheres
-
callqcomp.out_D16MGemt.gz:
Q_ext, Q_abs, Q_sca, <cos(theta)>, and <cos^2(theta)>
for spheres using
Maxwell Garnett effective medium theory (method MG_1 in Draine (2016)),
for 41 radii (0.001 micron to 10 micron) and 3501 wavelengths (1.0 cm to
10.0 A), uniformly spaced in log(radius) and log(wavelength)
-
planck_D16MGemt.out:
Planck-averaged efficiency factors Q_abs and Q_pr
for absorption and radiation pressure,
calculated for turbostatic graphite spheres for
25 selected radii from 0.001 micron to 10 micron, using effective
dielectric function MG_1 from Draine (2016), for radiation color
temperaturs from T = 10K to T=5x10^5 K.
Cross sections for turbostratic graphite spheroids
Scattering and absorption cross sections have been calculated for
spheroids composed of turbostratic graphite, using Maxwell Garnett
effective medium theory (method MG_1 in Draine 2016) to estimate
the effective dielectric function for turbostratic graphite
material. Efficiency factors Q_abs=C_abs/pi*aeff^2,
Q_ext=C_ext/pi*aeff^2, and Q_sca=C_sca/pi*aeff^2, where aeff = radius of
equal-volume sphere. Cross sections have been calculated using the
spheroid code of Voshchinnikov & Farafanov (1993) plus approximations
when size/wavelength is either very small or very large.
Cross sections are calculated for 3 orientations (jori=1-3)
of the spheroid symmetry axis "a" relative to the incident
linearly-polarized plane wave:
-
jori=1: k || a , E perp a
- jori=2: k perp a , E || a
- jori=3: k perp a , E perp a
Results are given for 169 sizes
[log10(a/um) from -3.50 to 0.70] and 1009 wavelengths
[log10(wave/um) from -1.04 to 4.00].
The files are in ascii, with the following structure:
- lines 5-26: list of radii rad(0-168)
- line 27: comment
- lines 28-154: list of wavelengths wave(0-1008)
- line 155: comment
- lines 156-64101: Qabs(jori=1-3,jrad=0-168,jwave=0-1008)
- line 64102: comment
- lines 64103-128048: Qext(jori=1-3,jrad=0-168,jwave=0-1008)
- line 128049: comment
- lines 128050-191995: Qsca(jori=1-3,jrad=0-168,jwave=0-1008)
Qabs, Qext, and Qsca are listed in the order used by Fortran, with
first index varying most rapidly: e.g., Qabs(1,0,0), Qabs(2,0,0),
Qabs(3,0,0), Qabs(1,1,0), Qabs(2,1,0), ... , Qabs(2,168,1008),
Qabs(3,168,1008)
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