Formation of Astrobiologically Important Molecules in

Extraterrestrial Environments

Ralf I. KaiserDepartment of Chemistry

University of Hawai’iHonolulu, HI 96822

kaiser@gold.chem.hawaii.eduhttp://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)