formation of astrobiologically important molecules in extraterrestrial environments ralf i. kaiser...
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Formation of Astrobiologically Important Molecules in
Extraterrestrial Environments
Ralf I. KaiserDepartment of Chemistry
University of Hawai’iHonolulu, HI 96822
[email protected]://www.chem.hawaii.edu/Bil301/welcome.html
Orion Constellation
Orion Nebula
H : 1 He : 0.1
O : C : N = 7 : 3 : 1 (0.001)
gas phase solid state99 % 1 %
carbonaceous and silicate-basednanoparticl es
= 10-
molecular clouds and cores
circumstellar envelopes
Interstellar Medium
T = 10 – 4000 K
= 102 – 109 cm-3
T = 10 K
= 10-11 cm-3
H-H
CH4, C2H2, C2H4, C2H6
H2O, H2S, NH3
CO, CO2
CH3OH, C2H5OH
CH3COCH3, H2CO,CH3CHO
HCOOH, CH3COOH
Amino Acid
Characteristics of a Chemical Reaction
1. exoergic vs. endoergic 2. no entrance barrier vs. barrier
3. binary vs. ternary reactions
The 70es – Bimolecular Ion-Molecule Reactions
k = 10-9 cm3s-1 (Herbst et. al)
O O+ + e-
O+ + H2 OH+ + H
OH+ + H2 OH2+ + H
OH2+ + H2 OH3
+ + H
OH3+ + e- H2O + H
simple hydrides in cold molecular clouds(CH4, NH3, H2O)
The 80es – Problems with Ion-Molecule Reactions
H C C C N
C2H2
C2H2+ + e-
C2H2+ + CN HCCCN+ + H
HCCCN+ + H2 H2CCCN+ + H
H2CCCN+ + e- HCCCN + H
The 80es – Problems with Ion-Molecule Reactions
[HCCCN] : [HCCNC] : [HNCCC]
240 : 8 : 1 (models)
1000 : 8 : 1 (TMC-1)
The 90es – Bimolecular Neutral-Neutral Reactions
CN(X2+) + CnHm CnH(m-1)CN + H
C2H(X2+) + CnHm CnH(m-1)C2H + H
C(3Pj) + CnHm C(n+1)H(m-1) + H
k = 10-10 cm3s-1 (Kaiser et al.; Smith et al.)
C2(X1g+) + CnHm C(n+2)H(m-1) + H
The 90es – Bimolecular Neutral-Neutral Reactions
Titan IRC+10216
H : 1 He : 0.1
O : C : N = 7 : 3 : 1 (0.001)
gas phase solid state99 % 1 %
carbonaceous and silicate-basednanoparticl es
= 10-
molecular clouds and cores
circumstellar envelopes
Interstellar Medium
T = 10 – 4000 K
= 102 – 109 cm-3
T = 10 K
= 10-11 cm-3
UV photons
cosmic ray particles
Cold Molecular Cloud B68
carbon dioxide carbon monoxide
water
methane ammonia
methanol
The late 90es – Grain-Surface Reactions
hopping
tunneling
Eley-Rideal
Langmuir-Hinshelwood
accretion
H + H H2
carbon dioxide carbon monoxidewater
methane ammonia
methanol
RTEaAek
The 00es - Galactic Cosmic Ray Processing
10 MeV
9 MeV
1. ionization
2. electronic excitation
3. vibrational excitation
4. electron attachment
cleavage of
chemical bonds
‘electronic’interaction
The 00es - Galactic Cosmic Ray Processing
1. Energy Conservation
10 eV transfer – 4.5 eV bond energy = 5.5 eV maximum kinetic energy
2. Angular Momentum Conservation
H atom (5.15 eV) versus CH3 radical (0.35 eV)
kinetic energy vibrational energy
Non-Equilibrium Chemistry
1. exoergic vs. endoergic 2. no entrance barrier vs. barrier
3. binary vs. ternary reactions
A* + BC
C2H4O Isomers
acetaldehyde ethylene oxide vinyl alcohol
H2O, CO, CO2, NH3, CH4, CH3OH
CO/CH4CO2/C2H4 H2O/C2H2
C2H4O Isomers
acetaldehyde ethylene oxide vinyl alcohol
H
C C
OHH
+ H
H
C C
OHH
H
a b
a
b
b
a
+
+ +
+C O
C
H
HHH
C O
H
C
HH O
C
H
Surface Scattering Machine
T = 10 – 350 K p = 810-11 torr
LET (5 keV e-) = 3 – 5 keV m-1 = LET (10 MeV H+)
30 min laboratory = 106 years in cold molecular cloud
1.electron source
2. cation source (positively charged particles)
Sources
3. pyrolytic radical source
4. tunable photon source
CO/CH4 Ice before Irradiation at 10 K
-0.10
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
10001500200025003000350040004500
Wavenumber (cm-1)
Ab
sorp
tio
n
45
29
= Methane
= Carbon Monoxide
43
01
42
47
42
03
36
49
30
18
30
03
29
06
28
17
21
34
21
42
20
89
15
29
13
08
25
95
-0.10
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
10001500200025003000350040004500
Wavenumber (cm-1)
Ab
sorp
tio
n
45
29
= Methane
= Carbon Monoxide
43
01
42
47
42
03
36
49
30
18
30
03
29
06
28
17
21
34
21
42
20
89
15
29
13
08
25
95
CO/CH4 Ice after Irradiation at 10 K
612 cm-1
2 (CH3 out of plane)
CO/CH4 Ice after Irradiation at 10 K
1853 cm-1
3 (HCO; CO stretch)
CO/CH4 Ice after Irradiation at 10 K
1725 cm-1
4 (CH3CHO; CO stretch)
QMS: CO/CH4 during Irradiation
H + H H2
CO/CH4 Ices after Irradiation at 10 K
H
C C
OHH
+ H
H
C C
OHH
H
a b
a
b
b
a
+
+ +
+C O
C
H
HHH
C O
H
C
HH O
C
H
[CH4-CO] [CH3…HCO] CH3CHO
Kinetics
(pseudo) 1st order kinetics
electron induced decomposition
[CH4-CO] [CH3…HCO] CH3CHO
Kinetics
[CH4-CO] [CH3…HCO] CH3CHOk1 k2
a = 2.32 (0.42) 1015 cm-2
k1<<k2 = 1.13 ( 0.29) 10-11
s-1
a = 2.32 (0.42) 1015 cm-2
k1<<k2 = 1.13 ( 0.29) 10-11
s-1
CH4 (X1A1) CH3(X2A2’’)
+H(2S1/2) CH4 (X1A1) CH3(X2A2
’’) +H(2S1/2)
CO (X1) +H(2S1/2) HCO (X2A’) CO (X1) +H(2S1/2) HCO (X2A’)
a = 3.87 (0.18) 1015 cm-2
k3 = 4.4 ( 0.37) 10-11 s-1
a = 3.87 (0.18) 1015 cm-2
k3 = 4.4 ( 0.37) 10-11 s-1
a = 3.39 (0.15) 1015 cm-2
k4 = 5.49 ( 0.73) 10-11 s-1
a = 3.39 (0.15) 1015 cm-2
k4 = 5.49 ( 0.73) 10-11 s-1
k3k3 k4k4
Kinetics
[CH4-CO] [CH3…HCO] CH3CHO
Electronic Structure Calculations
Osamura et al. 2004
C2H4O Isomers
acetaldehyde ethylene oxide vinyl alcohol
H2O, CO, CO2, NH3, CH4, CH3OH
CO/CH4CO2/C2H4 H2O/C2H2
CO2/C2H4 Ices after Irradiation at 10 K
0.00
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
21102115212021252130213521402145215021552160
Wavenumber (cm-1)
Ab
sorp
tion
2139
(ν 1
fro
m C
O)
2139 cm-1
1 (CO; stretch)
CO2/C2H4 Ices after Irradiation at 10 K
16801700172017401760
Wavenumber (cm-1)
0.000
0.005
0.010
0.015A
bsor
ptio
n
1723 cm-1
4 (CH3CHO; CO stretch)
CO2/C2H4 Ices after Irradiation at 10 K
850860870880890
Wavenumber (cm-1)
0.000
0.002
0.004
0.006
0.008
0.010A
bsor
ptio
n
868 cm-1
12 (c-C2H4O; ring)
Kinetics
(pseudo) 1st order kinetics
electron induced decomposition
[C2H4-CO2] [C2H4…O…CO] [C2H4O+CO]
C2H4 + O CH3CHO C2H4 + O CH3CHO
a = 2.10 (0.09) 1015 cm-2
k1 = 5.22 ( 0.37) 10-12 s-1
a = 2.10 (0.09) 1015 cm-2
k1 = 5.22 ( 0.37) 10-12 s-1
a = 1.77 (0.05) 1015 cm-2
k2 = 6.29 ( 0.34) 10-12 s-1
a = 1.77 (0.05) 1015 cm-2
k2 = 6.29 ( 0.34) 10-12 s-1
k1k1
Kinetics
0 5 10 15 20 25 30
Time (min)
0.0
0.5
1.0
1.5
2.0x1015
Mol
ecul
escm
-2
0 5 10 15 20 25 30
Time (min)
0.0
0.5
1.0
1.5x1015
Mol
ecul
escm
-2
C2H4 + O c-C2H4O C2H4 + O c-C2H4O
k2k2
Mechanism
+ OCC
H
HH
H
CC
H
HH
H
O
CC
H
HH
H
O
H3C H
O
CC
O
HH
H H
Mechanism
‘cone of acceptance’ favors attack of bond (formation of acetaldehyde and ethylene oxide)
Mechanisms
[CH4-CO] [CH3…HCO] CH3CHOa = 2.32 (0.42) 1015 cm-2
k = 1.13 ( 0.29) 10-11 s-1
a = 2.32 (0.42) 1015 cm-2
k = 1.13 ( 0.29) 10-11 s-1
[C2H4-CO2] [C2H4…O…CO] [C2H4O+CO]
a = 2.10 (0.09) 1015 cm-2
k = 5.22 ( 0.37) 10-12 s-1
a = 2.10 (0.09) 1015 cm-2
k = 5.22 ( 0.37) 10-12 s-1
a = 1.77 (0.05) 1015 cm-2
k = 6.29 ( 0.34) 10-12 s-1
a = 1.77 (0.05) 1015 cm-2
k = 6.29 ( 0.34) 10-12 s-1
CH3CHO c-C2H4O
kinetics versus dynamics
C2H4O Isomers
acetaldehyde ethylene oxide vinyl alcohol
H2O, CO, CO2, NH3, CH4, CH3OH
CO/CH4 CO2/C2H4H2O/C2H2
synchrotron irradiations are crucial to discriminate between O(3P) and O(1D)
H : 1 He : 0.1
O : C : N = 7 : 3 : 1 (0.001)
gas phase solid state99 % 1 %
carbonaceous and silicate-basednanoparticl es
= 10-
molecular clouds and cores
circumstellar envelopes
Interstellar Medium
T = 10 – 4000 K
= 102 – 109 cm-3
T = 10 K
= 10-11 cm-3
Crossed Molecular Beams Machine
Acknowledgements
Chris Bennett (UH, USA)
Corey Jamieson (UH, USA)
Prof. Nigel Mason (OU, UK)
Prof. Yoshihiro Osamura (Tokyo, Japan)