The Millimeter/Submillimeter Spectrum of the CCP (X2r) Radical

DeWayne T. HalfenSteward Observatory, Arizona Radio Observatory, University of Arizona

Dennis ClouthierDepartment of Chemistry, University of Kentucky

Lucy M. ZiurysDepartments of Chemistry and Astronomy, Steward Observatory, Arizona

Radio Observatory, University of Arizona

June 20, 2008

Why CCP ?Why CCP ?

• Chemical aspect– Dicarbides have 2 possible structures:

cyclic T-shaped or linear

– Cyclic: NaC2, MgC2, AlC2, SiC2 (Largo et al.

2004; Chasovskikh et al. 2007; Thaddeus et al. 1984)

– Linear: CCS, CCCl (Saito et al. 1987; Sumiyoshi et al. 2003)

• Astronomical Aspect– Five phosphorus-bearing molecules found in

circumstellar envelopes, including CP and HCP (Guélin et al. 1990; Agúndez et al. 2007; Milam et al. 2008)

– Multiple carbon-chain species present as well, up to C8

– CCP is next logical molecule to search for (see FD07)

Phosphorus-bearing

species in space

PN CP HCP

PO PH3

Are there more?

TA

* (K

) 0.00

0.01

-146 -86 -26 34 94

0.00

0.01

CP: N = 5 4 IRC +10216

J = 5.5 4.5

VLSR (km s-1)

J = 4.5 3.5

13CC3H

C4H

C4H

29SiC2C4H

U

NaCN

U

Milam et al. 2008

• Theoretical calculations by Largo et al. (1994), El-Yazal et al. (1997), and Sunahori, Wie, Clouthier (2007)– Predicted linear CCP structure and

2r ground state

– Calculated the bond lengths, dipole moment (3.3-3.6 D), and vibrational frequencies

• First detected in lab by Sunahori, Wie, Clouthier (2007)– Measured LIF and wavelength-

resolved emission spectrum of the 2–X2r transition

Sunahori, Wie, Clouthier 2007

Past Work on CCPPast Work on CCP

Millimeter-wave Direct Absorption SpectrometerMillimeter-wave Direct Absorption Spectrometer

Detector

RadiationSource

Gas Cell

Reactant

Gas-Phase Synthesis of CCPGas-Phase Synthesis of CCP

• Gas-phase P source– Glass oven in an

attachment at the end of the cell

– Heated red phosphorus to 300oC

• Added 1-2 mtorr of acetone free HCCH– Dry Ice/Acetone trap

necessary (-80oC)

• 40 mtorr of Ar carrier gas also added

• AC discharge – 200 W at 600 – Blue glow in cell Gas-phase P source

Ring Electrodes Glass Attachment

Sample Oven

Cooling Jacket+ -

Caution: Red P + heat in vacuum makes white P

0.6

0.4

0.2

0.0

410409408407406405404403402401400399x10

3

0.6

0.4

0.2

0.0

383382381380379378377376375374x10

3

0.6

0.4

0.2

0.0

397396395394393392391390389388387x10

3

0.6

0.4

0.2

0.0

370369368367366365364363362361x10

3

0.6

0.4

0.2

0.0

423422421420419418417416415414413412x10

3

J' = 32.5

J' = 31.5

J' = 30.5

J' = 29.5

J' = 28.5

Rotational Spectrum of CCP (X2r)

Rotational Spectrum of CCP (X2r)

• Initially searched 30 GHz– Used predictions based on

Sunahori et al. (2007) study

– Identified doublets decreasing in separation with increasing frequency

– = 1/2 of a 2r state

• Searched for = 3/2 state– Conditions optimized

– Another 25 GHz selectively scanned

– = 3/2 identified as doublet increasing in separation with increasing frequency

– v2 = 1 also observed

= 1/2

= 3/2 v2 = 1

CCP Search Stick Spectrum

• = 1/2 and 3/2 spin-orbit ladders, e and f lambda-doublets

• Phosphorus hyperfine I(P) = 1/2 observed at low frequency

133620133600133580

413305413285413265

273525273505273485

J = 10.5 9.5

J = 21.5 20.5

J = 32.5 31.5e f

e f

e f 10 9F = 11 1010 9F = 11 10

Frequency (MHz)

CCP (X2r) = 1/2

340221340201340181

532368532348532328

417133417113417093

J = 26.5 25.5

J = 32.5 31.5

J = 41.5 40.5

e f

e f

e/f

Frequency (MHz)

CCP (X2r) = 3/2

Halfen, Sun, Clouthier, Ziurys 2008

-30

-20

-10

0

10

20

30

40

50

7.5 12.5 17.5 22.5 27.5 32.5 37.5 42.5

L-t

ype

do

ub

ling

(M

Hz)

J'

L-type doubling vs. J'

= 1/2

= 3/2

413304413284413264

464090464070464050

438700438680438660

J = 32.5 31.5

J = 34.5 33.5

J = 36.5 35.5f e

e/f

e f

Frequency (MHz)

CCP (X2r) = 1/2

• 33 = 1/2 transitions measured from 120-540 GHz

• 18 = 3/2 transitions recorded from 301-545 GHz

• 113 lines measured

• Fine structure resolved for most transitions

Selected Rotational Frequencies of CCP (X 2r)

J J F F Parity obs obs - calc

10.5 9.5 11 10 1/2 e 133577.511 0.04410 9 1/2 e 133579.049 0.00811 10 1/2 f 133623.741 -0.00610 9 1/2 f 133625.600 0.016

21.5 20.5 a 1/2 e 273489.512 0.010a 1/2 f 273519.557 -0.019

26.5 25.5 a 3/2 e 340200.936 0.094a 3/2 f 340200.936 0.094

32.5 31.5 a 1/2 e 413281.401 -0.009a 1/2 f 413287.070 -0.009a 3/2 e 417112.006 -0.037

41.5 40.5 a 3/2 f 417113.597 0.034a 3/2 e 532346.287 0.019a 3/2 f 532349.624 -0.057

Transition Frequencies of CCP (X2r)Transition Frequencies of CCP (X2r)

Spectroscopic Constants for CCPParameter This work (MHz) Theoretical

B 6392.4138(26) 6390a, 6367b

D 0.0022595(22)H 9.50(59) x 10-9

A 4212195c

AD 40.536(10)AH -2.782(86) x 10-4

AL 4.8(2.3) x 10-9

p+2q 50.0127(96)(p+2q)D -0.015124(47)(p+2q)H 7.29(21) x 10-7

q 0.0109c

qD 6.57(17) x 10-5

h1/2 484.220(30)h1/2D 0.8337(91)d1/2 632.538(16)rms 0.050

a Sunahori et al. (2008) b El-Yazal et al. (1997) c Held fixed.

•

• Rotational constant B agrees well with theoretical predictions

• Lambda-doubling constant p+2q well determined– q held fixed, not defined (3) in

final fit

• Hyperfine splitting only observed in = 1/2 state– Only h1/2 and d1/2 could be

established

• Data analyzed to experimental accuracy of 50 kHz

mhfldsoroteffˆˆˆˆˆ HHHHH

Spectroscopic Analysis of CCPSpectroscopic Analysis of CCP

• Confirmed CCP linear molecule – More discussion of its structure next talk by M. Sun (FC03)

• With these rest frequencies, we found CCP in space– See talk FD07

• Many other interesting phosphorus species could be measured in the laboratory

Summary and Future WorkSummary and Future Work

• Lucy Ziurys

• Dennis Clouthier

• Emmy Tenenbaum

• Ming Sun

• Robin Pulliam

• Lindsay Zack

• Jessica Dodd

• Gilles Adande

• NASA Astrobiology Institute

• NSF Astronomy and Astrophysics Postdoctoral Fellowship

AcknowledgementsAcknowledgements