ASTRONOMICAL APPLICATIONS
OF NEW LINE LISTS FOR CN, C2
AND THEIR ISOTOPOLOGUES
P. F. Bernath
Department of Chemistry and Biochemistry,
Old Dominion University, Norfolk, VA
C. Sneden
Department of Astronomy, The University of
Texas at Austin, Austin, Texas
J. S. A. Brooke and R.S. Ram
Department of Chemistry, University of York,
Heslington, York, UK
Interstellar CN Violet 0-0
2
+
2
+
B Σ -X Σ
Diffuse
interstellar
cloud
absorption
towards the
star HD169454
Gredel et al.
AA, 251, 625
(1991)
Linelist is
needed to get
temperature
and abundance
(column
density).
[CN]/[13CN]=38
Trot = 3 K (same
temperature as the cosmic
background radiation)
Astronomical Requirements
From Beer-Lambert law:
I  I 0 exp  S g   10 Nl 
Need a lineshape function g(ν-ν10) (assumed to be Voigt, etc.)
and a line strength S’ given by (SI units at temperature T, from
Bernath, Spectra of Atoms and Molecules):
2π ν10 S J J 
 Elow 
 hν10 
S 
exp  
1  exp  

3ε0 hcQT
 kT 
 kT 
2
Therefore need a line position, ν10, partition function, QT
(calculated), line intensity, SJ′J″ (or S′), and the lower state
energy, Elow.
Linelist consists of (at a minimum): ν10, S′ or A10 and Elow for
each line
Selected New
Astronomical Linelists
1. MgH B'2Σ+-X2Σ+, A2Π-X2Σ+ GharibNezhad et al. MNRAS
432, 2043 (2013); 25,26MgH Hinkle et al. ApJS 207, 26
(2013).
2. CN, 13CN, C15N B2Σ+-X2Σ+, A2Π-X2Σ+, Brooke et al.
ApJS 210, 23 (2014); Sneden et al., ApJS (submitted).
3. C2, C13C d3Π-a3Π (Swan system), Brooke et al. JQSRT
124, 11 (2013); Ram et al. ApJS 211, 5 (2014).
4. CP A2П-X2Σ+, Ram et al. JQSRT 138, 107 (2014).
5. NH, vibration-rotation, Brooke et al. JCP (submitted).
6. OH, vibration-rotation (Meinel bands), Brooke et al.
JQSRT (in preparation).
7. CH, 13CH C2Σ+-X2Π, B2Σ--X2Π, A2Δ-X2Π, vibrationrotation, Masseron et al. AA (in press).
Sunspot MgH
A2Π-X2Σ+ 0-0
On Earth and in Sun
24Mg:25Mg:26Mg
abundance is 79:10:11.
The magnesium isotopic
ratios are probes of the
heavy element
enrichment of the
Universe.
25Mg and 26Mg are
produced during He
burning; 24Mg is
produced during carbon
burning. Low
abundances of heavy
elements will result in
more 24Mg relative to
25Mg and 26Mg.
Hinkle et al. ApJS 207, 26
(2013)
Start
Full Calculation Method
(James
Brooke)
Einstein As and f-values – line list with
Spectrum
Line
assignment
and fit
PGOPHER
Case (a) matrix elements
Hund’s case (b) to (a)
Molecular constants
fit
Equilibrium constants
RKR
1
Potential energy curve
End
positions and intensities
Case (b) vibrational wavefunctions and
transition dipole moment matrix elements
LEVEL
Start
Ab initio
+
Electronic (transition)
dipole moment
function
13
C C
3
3
d Π-a Π
(Swan system)
Ram et al. ApJS 211, 5 (2014)
Fit of lines of Amiot (1983) for 0-0 Swan System and Islami and
Amiot (1986), Amiot and Verges (1982) for Ballik-Ramsay
System (b3Σ--a3Π ) with PGOPHER. Used ab initio transition
dipole moment function for C2 from Brooke et al. JQSRT 124,
11 (2013). In addition used isotope relations as needed.
Carbon-Enhanced Metal
Poor Stars (CEMP)
 Big Bang created only the elements H, He and a trace of Li
13.7 billion years ago.
 After few hundred million years first stars form (“Population
III”) and heavy elements are synthesized by nuclear fusion,
neutron reactions and supernova explosions.
 Next generation of stars forms from interstellar clouds of
ejected material (“Population II”); then same cycle as above.
 Third generation of stars form like our Sun (“Population I”).
Metallicity:
Population I: [Fe/H]=~0; Population II: [Fe/H]<-1; Population III: [Fe/H]<-6
HE 0212-0557 is CEMP star with [Fe/H]=-3.45 (i.e., Fe is depleted
by more than 1000 relative to Sun) but [C/Fe]=1.8 (i.e., C is
enhanced relative to Fe by a factor of 100, relative to Sun).
12C/13C is 3.5 (solar is 90). Probably mass transfer occurred from
an AGB star in a binary system. Sneden’s MOOG code used.
CN B2Σ+-X2Σ+ Δv=+2 Sequence
CN lab spectra were recorded by S. Davis with Kitt Peak FTS using a microwave
discharge of nitrogen with a trace of methane. Data was analyzed in a series of
papers: Ram et al. JMS 263, 82 (2010); Ram et al. ApJS 188, 500 (2010); Ram
& Bernath, ApJ 194, 34 (2011); Colin & Bernath, JMS 273, 30 (2012).
Transition dipole moment calculated by Schwenke used to generate linelists for
CN, 13CN, C15N B2Σ+-X2Σ+, A2Π-X2Σ+ transitions by Brooke et al. ApJS 210, 23
(2014); Sneden et al., ApJS (submitted).
Solar CN
(Fraunhofer
Lines)
13CN,
C15N
B2Σ+-X2Σ+,
CN,
A2Π-X2Σ+, Brooke et al. ApJS
210, 23 (2014); Sneden et al.,
ApJS (submitted).
Trot = 6000 K in the solar
photosphere; [CN]/[13CN]=90,
same as on Earth;
B2Σ+-X2Σ+, 0-0
A2Π-X2Σ+, 2-0
“Absolute” abundance is:
log ε(X) = log10(NX/NH) + 12
Asplund et al. (2009)
recommend log ε(N) =
7.83±0.05
Absorption in photosphere of the Sun
L. Wallace, Kitt Peak Solar Atlas
A2Π-X2Σ+, 0-0
Nitrogen
Abundance
of Two
CEMP Stars
CN B2Σ+-X2Σ+, 0-1 band
(Sneden et al. ApJS,
submitted)
CH, A2Δ-X2Π Transition (G band)
Constants for v’=4
and 5 derived from
stellar spectra by
Masseron et al. AA
(in press).
CH in
CEMP
Stars
CH, A2Δ-X2Π,
Masseron et al.
AA (in press);
4-4 and 5-5
bands identified
for the first time
A2Δ-X2Π 5-5
A2Δ-X2Π 4-4
Solar CH (1-0 Fundamental)
ACE solar spectrum: Hase et
al. JQSRT 111, 521 (2010)
Herman-Wallis effect must be
included using LEVEL (i.e., J-dep.
of vibrational wavefunction)
APOGEE: Apache Point Observatory
Galactic Evolution Experiment
APOGEE will survey over 100,000 red giant stars and record spectra with R~22,500 in
the 1.51-1.70 μm region to obtain abundance of 15 chemical species.