STUDIES OF THE FORMATION OF CARBONYL SULFIDE IN ION-IRRADIATED ICES

Robert F. FerranteMorgan M. SpiliotisU.S. Naval Academy

Marla H. MooreNASA/Goddard Space Flight Center

Reggie L. HudsonEckerd College

61st International Symposium on Molecular SpectroscopyThe Ohio State University

June 2006

Ehrenfreund, P. and Fraser, H, “Ice Chemistry in Space”, Solid State Astronomy,NATO ASI Series, V. Pirronello and J. Krelowski, eds., Kluwer Academic Publ. (2002).

 

ASTRONOMICAL OBSERVATIONS OF OCS

H+ beam from vdGaccelerator

2500 2000 1500 1000

0.0

0.2

0.4

0.6

C3O2 C2OHCO

CS2

after irradiation

before irradiation

9.0 K; CO:H2S = 5:1dose = 1.0x1014 H+/cm2

OCS

COCO2

H2S

IRRADIATION OF H2S IN CO

Rela

tive

Abso

rban

ce

Wavenumbers (cm-1)

2500 2000 1500 1000

-0.1

0.0

0.1

0.2

0.3

SOSO3

9.0 K; CO:SO2 = 5:1dose = 1.0x1014 H+/cm2

OCSSO2

SO2

COCO2

after irradiation

before irradiation

IRRADIATION OF SO2 IN CO

Rela

tive

Abso

rban

ce

Wavenumbers (cm-1)

2500 2000 1500 1000

-0.1

0.0

0.1

0.2

0.3

0.4

0.5

C3S2

C3S2CS

OCS

9.0 K; CO:CS2 = 5:1dose = 1.0x1014 H+/cm2

after irradiation

before irradiation

CO

CO2

CS2

IRRADIATION OF CS2 IN CO

Rela

tive

Abso

rban

ce

Wavenumbers (cm-1)

0.0 1.0x1014 2.0x1014 3.0x1014 4.0x1014

0.00

0.02

0.04

0.06

0.08

0.10

SO2

CS2

H2S

T~10 K

PRODUCTION OF OCS BY PROTON IRRADIATION

No

rmal

ized

OCS

Col

umn

Dens

ity (m

olec

OCS

/ in

itial

ato

m S

)

Radiation Dose (H+/cm2)

CO : H2S CO : CS2 CO : SO2 CO2 : H2S CO2 : CS2 CO2 : SO2

0 5 10 15 20 25 30

-2.5

-2.0

-1.5

-1.0

-0.5

0.0 CS2

SO2

H2S

OCSpure icesT~10 K

RADIATION DESTRUCTION OF SULFUR COMPOUNDS

Ln (N

orm

. Col

umn

Dens

ity)

Dose (eV/molec)

2200 2000 1800 1600 1400 1200 1000 800 600

-0.4

-0.3

-0.2

-0.1

0.0

0.1

0.2 COOCS2 SO2

SO2 CS2

CS2T~10K

1.5x1014 H+/cm2

1.0x1014 H+/cm2

5.0x1013 H+/cm2

2.5x1013 H+/cm2

1.0x1013 H+/cm2

before irradiation

IRRADIATION OF PURE OCS

Rela

tive

Abso

rban

ce

Wavenumbers (cm-1)

0 20 40 60 80 100 120 140 160

0.0

0.2

0.4

0.6

0.8

1.0

1.2

SO2H2SCO CO2

THERMAL BEHAVIOR OF OCS PRODUCT

Norm

aliz

ed A

rea

OCS

205

0 cm

-1 B

and

Temperature (K)

CO:H2S CO2:H2S CO:SO2 CO2:SO2

RESULTS AND CONCLUSIONS

OCS is readily formed by solid-state processes in low-temperature ices subjected to proton irradiation

- additional thermal activation not required- H2S > SO2 > CS2 as sulfur source

OCS is relatively unstable to destruction by irradiation

- significantly more labile than other S species:

OCS > H2S >> SO2 > CS2

- readily forms SO2 and CS2 on prolonged exposure

OCS formation enhanced by thermal processing in some systems