studies of the formation of carbonyl sulfide in ion-irradiated ices robert f. ferrante morgan m....
DESCRIPTION
H + beam from vdG acceleratorTRANSCRIPT
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