63 rd International Symposium on Molecular Spectroscopy June 16-20, 2008
13
2 Π r
D. T. Halfen, L. M. Ziurys
Dept. of Chemistry
Dept. of Astronomy
Steward Observatory
University of Arizona
J.C. Pearson, and B.J. Drouin
Jet Propulsion Laboratory
California Institute of Technology
F = 3/2 3/2
F = 3/2 5/2
CD (X
2  r
):

J = 1/2

3/2+
F = 1/2 1/2
F = 1/2 3/2
*
439.250
F = 3/2 5/2
439.260
439.270
439.280
J = 1/2+ 3/2

F = 3/2 3/2
F = 1/2 3/2
F = 1/2 1/2
439.785
439.795
439.805
Frequency (GHz)
439.815

63 rd International Symposium on Molecular Spectroscopy June 16-20, 2008
• CH observed in many interstellar environments
• Tracer of Diffuse Gas at UV, optical wavelengths

One of original four interstellar species

Detected via electronic spectra
• Observed optically in Comets
• Also found towards many Denser Clouds
 studied via lambda-doubling transition in
J = ½ level ( 3 hyperfine components)
 limited observations of rotational transitions in Far-IR
(Kuiper Airborne Observatory)
CH: F-X Band:
X Per
CH: Hale-Bopp
CH at 3 GHz: hf components of
Lambda-doublet

63 rd International Symposium on Molecular Spectroscopy June 16-20, 2008
13
• CH in many interstellar environments
• Fundamental building block of interstellar carbon chemistry
• Useful to measure 12 C/ 13 C ratios via 13 CH/ 12 CH
 tracer of Galactic Chemical Evolution
• D/H ratio also significant
 indicator of fractionation
 follow chemical pathways
• Effective avenue to measure such ratios

Observing rotational spectra

Become very feasible with
Herschel, SOFIA
KAO CH spectrum
Herschel Space Observatory

63 rd International Symposium on Molecular Spectroscopy June 16-20, 2008
Energy Level Diagram: case (b)
Past Rotational Spectroscopy
CD:
• Brown and Evenson (1989)
• Wienkoop et al. (2003)

LMR, FTIR measurements
 in mid, far IR
13 CH:
• Davidson et al (2004)

LMR of rotational transitions
• McCarthy et al. (2006)

FTMW measurements of several lambda-doublets with hf
• This work: measure rotational transitions directly
CD:
N = 1 →2
CD and 13 CH:
N = 1 →1

63 rd International Symposium on Molecular Spectroscopy
Are such measurements necessary ??
CH
3
CH
2
CN
0.3
0.2
0.1
0.5
0.4
0.0
-0.1
143.0
143.2
U
U
143.4
x10
3
Frequency (GHz)
June 16-20, 2008
CH
3
CH
2
CN
SgrB2(N)
U
U
U
U
U
143.6
143.8
U

63 rd International Symposium on Molecular Spectroscopy June 16-20, 2008
Millimeter Direct Absorption with AC Longitudinal Discharge

63 rd International Symposium on Molecular Spectroscopy June 16-20, 2008
Source developments thanks to Herschel/HIFI sweep synthesizer
YIG filter mm-wave module
MMIC amps submm multipliers
HP8340b M1611/2D
83558A waveguide feedhorns sample cell
He cooled detector gas Si sample modulation
AM/FM/TM tuning voltage
DAQ
GPIB
PC vacuum pump sync
HP FG waveform generator
SR830 lock-in-amplifier pre-amp
Direct Absorption, DC discharge

63 rd International Symposium on Molecular Spectroscopy
Detector
Arizona System
June 16-20, 2008
Reactant
Gas Cell
Radiation
Source

63 rd International Symposium on Molecular Spectroscopy June 16-20, 2008
13
• Arizona Studies
• Precursor gas:
CD
4 or 13 CH
4
–Pressure: 1-5 mTorr
• Carrier Gas: 40 mTorr
Argon
• AC discharge for
–200 W at 600 W
–Pink-purple glow
• JPL CD synthesis
- 5 mTorr CH
4
/20 mTorr
D
2 with 100 mTorr He
- DC discharge

63 rd International Symposium on Molecular Spectroscopy
F = 3/2 3/2
F = 3/2 5/2
CD (X
2  r
):

J = 1/2

3/2+
F = 1/2 1/2
F = 1/2 3/2
Arizona
Data
June 16-20, 2008
CD (X
2  r
): N = 2

1
J = 2.5


1.5

F = 3.5

2.5
F = 2.5

1.5
JPL
Data
*
439.250
F = 3/2 5/2
439.260
439.270
439.280
J = 1/2+ 3/2

F = 3/2 3/2
F = 1/2 3/2
F = 1/2 1/2
Hyperfine
Structure
Resolved in
N = 1
→1
Spectrum
915844
J = 2.5


1.5

915854 915864
F = 3.5

2.5
F = 2.5

1.5
439.785
439.795
439.805
Frequency (GHz)
439.815
Halfen et al
Ap.J., in press
916944 916954
Frequency (MHz)
916964

63 rd International Symposium on Molecular Spectroscopy
Arizona Data
J = 1/2

3/2+
13
CH (X
2  r
):

F
1
= 1 2
F = 3/2 5/2
F
1
= 1 2
F = 1/2 3/2
June 16-20, 2008
F
1
= 0 1
F = 1/2 1/2
F = 1/2 3/2
531.88
531.93
J = 1/2+ 3/2

531.98
F
1
= 0 1
F = 1/2 3/2
532.03
532.08
F
1
= 1 2
F = 3/2 5/2
532.13
532.18
F
1
= 1 2
F = 1/2 3/2
*
532.23
535.88
535.93
535.98
536.03
536.08
Frequency (GHz)
536.13
536.18
536.23
Resolved 13 C and H hf structure

63 rd International Symposium on Molecular Spectroscopy June 16-20, 2008
CD
Observed Transition Frequencies of CD (X 2
N
 
N

J
 
J

F
 
F

 r
)
Parity n obs
(MHz)
1

1 1.5

0.5
1.5

1.5
+
 
439255.608 a
2.5

1.5
+
 
439257.449
a
0.5

0.5
+
 
439271.905
a
1.5

0.5
+
 
439272.694
a
1

1 1.5

0.5
2.5

1.5
 
+ 439794.923
1.5

1.5
 
+ 439800.005
1.5

0.5
 
+ 439803.008
0.5

0.5
 
+ 439806.093
2

1 1.5

1.5
0.5

1.5
 
+ 884764.787
a
0.5

0.5
 
+ 884764.787
a
1.5

2.5
 
+ 884770.707
a
1.5

1.5
 
+ 884770.707
a
1.5

0.5
 
+ 884772.903
a
2.5

1.5
 
+ 884781.449
a
2.5

2.5
 
+ 884781.449
a
2

1 1.5

1.5
2.5

2.5
+
 
887230.840
2

1 2.5

1.5
3.5

2.5
 
+ 915851.970
a
2.5

1.5
 
+ 915854.900
a
2

1 2.5

1.5
3.5

2.5
+
 
916954.496
a
2.5

1.5
+
 
916954.496
a a Blended lines.
0.039
0.093
-0.906
0.984
-0.680
0.517
-1.095
0.570
0.000
-0.196
0.196
0.617
-0.617
n obs
n calc
(MHz)
-0.076
0.101
0.093
-0.117
-0.027
0.003
-0.015

63 rd International Symposium on Molecular Spectroscopy June 16-20, 2008
Observed Transition Frequencies of 13 CH (X 2
 r
) a
N
 
N

J
 
J

F
1
 
F
1

F
 
F

Parity n obs
(MHz)
1

1 1.5

0.5
1

1 0.5

1.5
+
 
531859.975
1

1 1.5

1.5
+
 
531862.711
1

1 0.5

0.5
+
 
531910.901
13 CH
1

1 1.5

0.5
+
 
531913.471
2

1 1.5

1.5
+
 
532083.360
2

1 2.5

1.5
+
 
532086.251
2

1 1.5

0.5
+
 
532134.740
1

0 0.5

0.5
+
 
532224.939
1

0 1.5

0.5
+
 
532227.528
1

1 1.5

0.5
1

0 1.5

0.5
 
+ 536005.094
1

0 0.5

0.5
 
+ 536024.969
1

1 1.5

1.5
 
+ 536026.643
1

1 0.5

1.5
 
+ 532046.477
1

1 0.5

0.5
 
+ 536057.826
2

1 2.5

1.5
 
+ 536101.144
2

1 1.5

1.5
 
+ 536121.035
2

1 1.5

0.5
 
+ 536132.344
a Coupling scheme: J = N + S ; F
1 spins, respectively.
= J + I
1
; F = F
1
+ I
2
; where I
1 and I
2 n obs
n calc
(MHz)
-0.565
-0.182
-0.142
0.076
-0.238
0.316
0.640
-0.479
-0.242
0.173
0.567
0.144
0.497
0.133
-0.373
0.030
-0.374
are the 13 C and H nuclear

63 rd International Symposium on Molecular Spectroscopy June 16-20, 2008
B
D
H
A g p p
D q q
D
a (D) b
F
(D)
c (D)
d (D) eqQ(D)
C Held fixed.
Spectroscopic Constants for CD (X 2
 r
)
Parameter This work (MHz) Wienkoop et al. ( MHz)
230895.03(80)
12.698(90)
0.0004751 c
842308.59
c
-424.049(91)
544.89(27)
-0.047
c
339.424(97)
-0.082(34)
8.74(27)
-8.797(72)
9.26(81)
7.054(87)
-0.69(41)
230896.08(13)
12.8216(36)
0.0004751
c
842308.59(90)
-423.80(23)
544.41(57)
-0.047(39)
339.45(18)
-0.0761(69)
8.05(99)
-8.99(87)
8.9(1.6)
7.06(90)
-
• Deuterium eqQ determined
• Improved D hf constants
• Improved fine structure constants
• Good agreement with past work

63 rd International Symposium on Molecular Spectroscopy
Parameter
Spectroscopic Constants for 13 CH (X 2
 r
) a
This work (MHz) McCarthy et al. (MHz) Davidson et al. (MHz)
A g p
B
D p
D q q
D
a ( 13 C) b
F
( 13 C)
c ( 13 C)
d ( 13 C) d
D
( 13 C)
a (H) b
F
(H)
c (H)
d (H) d
D
(H)
422962.011(18)
43.3319
a
843799.80
a
-765.26
a
997.674(53)
-0.298
a
1146.056(10)
-0.4476
d
217.752(85)
41.989(91)
-129.83(19)
276.67(16)
-0.393(24)
54.410(88)
-57.60(10)
57.19(23)
43.841(41)
0.0836(50)
422966.125(270)
43.3319(150)
843799.80(1.14)
-765.26(33)
998.12(48)
-0.298(54)
1145.971(81)
-0.4476(78)
218.20(57)
41.83(90)
-131.02(1.17)
275.14(1.20)
-0.166(177)
54.2169(39)
-57.855 a
56.266
a
43.836(54)
0.0826(78)
422966.021(285)
43.3291(144)
843799.44(1.23)
-765.10(36)
998.39(72)
-0.305(69)
1146.073(132)
-0.4554(117)
218.10(1.26)
41.99(84)
-131.0(3.6)
275.54(78)
54.006
a
-57.777 a
56.52
a
43.513
a a Held fixed.
June 16-20, 2008
• Proton b
F and c established
• Improved 13 C hyperfine and lambda-doubling constants
• 4 MHz discrepancy in B

63 rd International Symposium on Molecular Spectroscopy June 16-20, 2008
• Lowest energy rotational transitions of CD and 13 CH measured
• Precision of 200-500 kHz
• Determination of hyperfine parameters (eqQ(D), b
F
(H), c(H))
• Improvement of other spectroscopic constants
• Important for upcoming Herschel, SOFIA observations
• Used to establish 12 C/ 13 C ratios
• Degree of deuterium enhancement in fundamental building block CH
ACKNOWLEDGEMENTS:
NASA Lab Astrophysics Program