1

July the 4th 2016ISWA 2016 - Campinas, SP, Brazil

Elisabetta MicelottaUniversity of Helsinki

Energetic processing of complex carbonaceous compounds

2

Complex carbon compounds

a-C:H nanoparticlesPAHs C60 C70

3

E = 10 eV - 3 keV

E = 5 - 50 eV

E = 10 eV - 10 keV

E = 5 MeV/nuc - 10 GeV

Ions & Electrons(H, He, CNO)

Photons

How?Processing occurs via

interactions with these projectiles

Energetic processing

UV: E= 6 - 15 eV

X-rays: E = 0.3 - 10 keV

4

NGC 6744

Solar System

Earth

Young star LL Ori Red Spider Nebula - PN

Bullet Cluster - merging

SN 1006

Cygnus A - radio lobes PhysOrg.com

NASA/ESA, Hubble Heritage

Where?

5

Adapted from Micelotta et al. 2010b, A&A, 510, A37

vSHOCK ~ 600 km/s

Temperature of gas:

T ~ 5.8x106 K

Thermal motion: E = 500 eV

Nc = 50

Electrons

Ions

PAHs in hot shocked gas: M82

τ0 =10 yr

Destroyed unless protected

6

PAHs in M82: add X-rays + CRs

Micelotta et al. 2011, A&A, 526, A52 Cosmic Rays: E = 5 MeV - 10 GeV

107

108

109

100 1000

TOTA

L 0

(yr)

NC

M82galactic wind

T0 = 7.5 eVE0 = 4.6 eV

X−rays timescale(lower limit)

f = 0.5f = 1.0

Circulation lifetimeStarburst − X−rays

7

Ions - C60 collisions

Energy incident ion (eV)

σ (Å

2 at

om-1

)

100

101

102

100 101 102 103 104 105

H −> CT0 = 15 eV

S0nSn

100

101

102

100 101 102 103 104 105

He −> CT0 = 15 eV

S0nSn

100

101

102

100 101 102 103 104 105

C −> CT0 = 15 eV

S0nSn

10−2

10−1

100

100 101 102 103 104 105

H −> CT0 = 15 eV

10−2

10−1

100

100 101 102 103 104 105

He −> CT0 = 15 eV

10−2

10−1

100

100 101 102 103 104 105

C −> CT0 = 15 eV

Micelotta et al. 2013, Proc. IAU Symp. 297, 339

8

NANOPARTICLE

+ UV photons

C104H80

HOT

giant cage

SHRINKING

down to C60

STABLE

C2

C2

C2

~C74 C60

Micelotta et al. 2012, ApJ, 761, 35

NEW MECHANISM!Conventional routes DO NOT WORK ⟹

C60 formation in space

9

Photo-processing Aromatic Infrared Bands - Proposed carriers

Flux

den

sity

λ (µm)a-C nanoparticles

“Astronomical” PAHs

“Classical” PAHs

Diffuse medium

10

Photo-processing

Mathis, J. S., et al. 1983, A&A, 128, 212 Galliano, F., et al. 2005, A&A, 434, 867

ISRF

DISSOCIATION

ABSORPTION

properties

EMISSION

properties

PARTICLE SIZE

modification

11

Photo-absorption cross sectionOptical - UV

Micelotta, Jones & Juvela 2016, in prep.Verstraete, L. & Léger, A. 1992, A&A, 266, 513 Li, A. & Draine, B. T. 2001, ApJ, 554, 778 Jones, A. P. 2012, A&A, 542, A98

12

Dissociation probability

• STATISTICAL fragmentation instead of IR emission

• All particles treated as PAHs

• Use of FORMALISM developed for PAHs to treat dissociation induced by ELECTRON COLLISIONS in shocks/hot gas (Micelotta et al. 2010a,b)

Micelotta, Jones & Juvela 2016, in prep.

13

Modified size distributionsThe effect of photo-dissociation &

initial grain size distribution

EACH KIND of particle with its

“NATIVE” initial distribution

14

Infrared emissionFrom photo-processed species and size distributions

DustEM implementation (Compiègne et al. 2011)

15

Infrared emissionFrom photo-processed species and size distributions

Note the SUPPRESSION of the 3.3 - 3.4 µm complex in NANOPARTICLES emission

16

Conclusions & Perspectives

•Energetic processing has multiple implications and needs detailed analysis.

•Analytical models important for astrophysics.

• Interconnection PAHs - fullerenes - nanoparticles.

•Theory & Experiments & Observations.

•New experimental facilities + telescopes (JWST).

17

Thank you!

Collaborators

• X. Tielens (STRW Leiden)

• A. Jones (IAS Orsay)

• M. Juvela (University of Helsinki)

• E. Peeters, J. Cami, G. Fanchini (U. of Western Ontario)

• J. Bernard-Salas (Open University)

• H. Zettergren, H. Cederquist, H. Schmidt (Stockholm University)

18

Sn(E) =

Z Tm

T0

d�(E, T ) · T

= 4⇡ aU Z1Z2 e2 M1M1 +M2

sUn (")

"1�

✓E0nE

◆1�m#

V (r) / r�1/m

dE

dR= N Sn(E)

Cm E�m T�1�m dT 0 . T . Tm

Stopping power Nuclear stopping

cross section

Atomic number density

Transferred

energy

ZBL Universal

screening length

ZBL Universal reduced

stopping cross section

Cross section

Threshold effectS0n(E) NO thresholdMicelotta et al.

2010a, A&A,

510, A36

19

�(E) =

Z Tm

T0

d�(E, T )

= 4⇡ aU Z1Z2 e2 M1M1 +M2

sUn (")1�mm

1

� E

"✓E0nE

◆�m� 1

#

hT (E)i = Sn(E)�(E)

= hT (E)i = m1�m �

E1�m � E1�m0nE�m0n � E�m

S0n(E) NO threshold

Total cross section

Average

transferred

energy Micelotta et al. 2010a, A&A, 510, A36

20

E. R. Micelotta et al.: PAH processing in interstellar shocks

100

101

102

100 101 102 103 104

Sn

(eV

Å2

atom

−1),

(

eV)

Energy Incident Ion (eV)

H −> CT0 = 7.5 eV

S0nSn

10−2

10−1

100

100 101 102 103 104

σ (

Å2

atom

−1)

Energy Incident Ion (eV)

H −> CT0 = 7.5 eV

σ

100

101

102

100 101 102 103 104

Sn

(eV

Å2

atom

−1),

(

eV)

Energy Incident Ion (eV)

He −> CT0 = 7.5 eV

S0nSn

10−2

10−1

100

100 101 102 103 104σ

(Å

2 at

om−1

)

Energy Incident Ion (eV)

He −> CT0 = 7.5 eV

σ

100

101

102

100 101 102 103 104

Sn

(eV

Å2

atom

−1),

(

eV)

Energy Incident Ion (eV)

C −> CT0 = 7.5 eV

S0nSn

10−2

10−1

100

100 101 102 103 104

σ (

Å2

atom

−1)

Energy Incident Ion (eV)

C −> CT0 = 7.5 eV

σ

Fig. 2. The nuclear stopping cross section S n(E), the total cross section σ(E) and the average energy transferred ⟨T (E)⟩ calculated for H, Heand C ions impacting on a carbon atom. The curves are calculated for the threshold energy T0 = 7.5 eV. The nuclear stopping cross section S 0ncorresponding to T0 = 0 (no threshold) is shown for comparison. The two vertical lines indicate the limiting energies for the incident ion. Theseare defined as the kinetic energies of the projectile when its velocity vp equals 34 (vS1,S2), where vS1 = 50 km s

−1 and vS2 = 200 km s−1 are the lowestand highest shock velocities considered in this study.

value of Td ∼ 15−20 eV seems appropriate for the perpendiculardirection. The in-plane value, however, could be much higher,presumably above 30 eV.

Instead of graphite, fullerenes and carbon nanotubes may bea better analog for PAH molecules. For fullerene, Td has beenfound between 7.6 and 15.7 eV (Füller & Banhart 1996). Single

Page 5 of 19

E. R. Micelotta et al.: PAH processing in interstellar shocks

100

101

102

100 101 102 103 104

Sn

(eV

Å2

atom

−1),

(

eV)

Energy Incident Ion (eV)

H −> CT0 = 7.5 eV

S0nSn

10−2

10−1

100

100 101 102 103 104

σ (

Å2

atom

−1)

Energy Incident Ion (eV)

H −> CT0 = 7.5 eV

σ

100

101

102

100 101 102 103 104

Sn

(eV

Å2

atom

−1),

(

eV)

Energy Incident Ion (eV)

He −> CT0 = 7.5 eV

S0nSn

10−2

10−1

100

100 101 102 103 104σ

(Å

2 at

om−1

)

Energy Incident Ion (eV)

He −> CT0 = 7.5 eV

σ

100

101

102

100 101 102 103 104

Sn

(eV

Å2

atom

−1),

(

eV)

Energy Incident Ion (eV)

C −> CT0 = 7.5 eV

S0nSn

10−2

10−1

100

100 101 102 103 104

σ (

Å2

atom

−1)

Energy Incident Ion (eV)

C −> CT0 = 7.5 eV

σ

Fig. 2. The nuclear stopping cross section S n(E), the total cross section σ(E) and the average energy transferred ⟨T (E)⟩ calculated for H, Heand C ions impacting on a carbon atom. The curves are calculated for the threshold energy T0 = 7.5 eV. The nuclear stopping cross section S 0ncorresponding to T0 = 0 (no threshold) is shown for comparison. The two vertical lines indicate the limiting energies for the incident ion. Theseare defined as the kinetic energies of the projectile when its velocity vp equals 34 (vS1,S2), where vS1 = 50 km s

−1 and vS2 = 200 km s−1 are the lowestand highest shock velocities considered in this study.

value of Td ∼ 15−20 eV seems appropriate for the perpendiculardirection. The in-plane value, however, could be much higher,presumably above 30 eV.

Instead of graphite, fullerenes and carbon nanotubes may bea better analog for PAH molecules. For fullerene, Td has beenfound between 7.6 and 15.7 eV (Füller & Banhart 1996). Single

Page 5 of 19

E. R. Micelotta et al.: PAH processing in interstellar shocks

100

101

102

100 101 102 103 104

Sn

(eV

Å2

atom

−1),

(

eV)

Energy Incident Ion (eV)

H −> CT0 = 7.5 eV

S0nSn

10−2

10−1

100

100 101 102 103 104

σ (

Å2

atom

−1)

Energy Incident Ion (eV)

H −> CT0 = 7.5 eV

σ

100

101

102

100 101 102 103 104

Sn

(eV

Å2

atom

−1),

(

eV)

Energy Incident Ion (eV)

He −> CT0 = 7.5 eV

S0nSn

10−2

10−1

100

100 101 102 103 104σ

(Å

2 at

om−1

)

Energy Incident Ion (eV)

He −> CT0 = 7.5 eV

σ

100

101

102

100 101 102 103 104

Sn

(eV

Å2

atom

−1),

(

eV)

Energy Incident Ion (eV)

C −> CT0 = 7.5 eV

S0nSn

10−2

10−1

100

100 101 102 103 104

σ (

Å2

atom

−1)

Energy Incident Ion (eV)

C −> CT0 = 7.5 eV

σ

Fig. 2. The nuclear stopping cross section S n(E), the total cross section σ(E) and the average energy transferred ⟨T (E)⟩ calculated for H, Heand C ions impacting on a carbon atom. The curves are calculated for the threshold energy T0 = 7.5 eV. The nuclear stopping cross section S 0ncorresponding to T0 = 0 (no threshold) is shown for comparison. The two vertical lines indicate the limiting energies for the incident ion. Theseare defined as the kinetic energies of the projectile when its velocity vp equals 34 (vS1,S2), where vS1 = 50 km s

−1 and vS2 = 200 km s−1 are the lowestand highest shock velocities considered in this study.

value of Td ∼ 15−20 eV seems appropriate for the perpendiculardirection. The in-plane value, however, could be much higher,presumably above 30 eV.

Instead of graphite, fullerenes and carbon nanotubes may bea better analog for PAH molecules. For fullerene, Td has beenfound between 7.6 and 15.7 eV (Füller & Banhart 1996). Single

Page 5 of 19

E. R. Micelotta et al.: PAH processing in interstellar shocks

100

101

102

100 101 102 103 104

Sn

(eV

Å2

atom

−1),

(

eV)

Energy Incident Ion (eV)

H −> CT0 = 7.5 eV

S0nSn

10−2

10−1

100

100 101 102 103 104

σ (

Å2

atom

−1)

Energy Incident Ion (eV)

H −> CT0 = 7.5 eV

σ

100

101

102

100 101 102 103 104

Sn

(eV

Å2

atom

−1),

(

eV)

Energy Incident Ion (eV)

He −> CT0 = 7.5 eV

S0nSn

10−2

10−1

100

100 101 102 103 104σ

(Å

2 at

om−1

)

Energy Incident Ion (eV)

He −> CT0 = 7.5 eV

σ

100

101

102

100 101 102 103 104

Sn

(eV

Å2

atom

−1),

(

eV)

Energy Incident Ion (eV)

C −> CT0 = 7.5 eV

S0nSn

10−2

10−1

100

100 101 102 103 104

σ (

Å2

atom

−1)

Energy Incident Ion (eV)

C −> CT0 = 7.5 eV

σ

Fig. 2. The nuclear stopping cross section S n(E), the total cross section σ(E) and the average energy transferred ⟨T (E)⟩ calculated for H, Heand C ions impacting on a carbon atom. The curves are calculated for the threshold energy T0 = 7.5 eV. The nuclear stopping cross section S 0ncorresponding to T0 = 0 (no threshold) is shown for comparison. The two vertical lines indicate the limiting energies for the incident ion. Theseare defined as the kinetic energies of the projectile when its velocity vp equals 34 (vS1,S2), where vS1 = 50 km s

−1 and vS2 = 200 km s−1 are the lowestand highest shock velocities considered in this study.

value of Td ∼ 15−20 eV seems appropriate for the perpendiculardirection. The in-plane value, however, could be much higher,presumably above 30 eV.

Instead of graphite, fullerenes and carbon nanotubes may bea better analog for PAH molecules. For fullerene, Td has beenfound between 7.6 and 15.7 eV (Füller & Banhart 1996). Single

Page 5 of 19

Energy incident ion (eV) Energy incident ion (eV)

σ (Å

2 at

om-1

)

S n (

eV Å

2 at

om-1

) (e

V)

E2E1

Micelotta et al. 2010a, A&A, 510, A36

21

Te� ' 2000✓Te(eV)

NC

◆0.4 ✓1 � 0.2 E0(eV)

Te(eV)

◆

P (nmax

) =

k0

exp [�E0

/k Tav

]

kIR

/(nmax

+ 1)

Te(⇥) = 27.2116

Z R/ sin �

�R/ sin �v �(rs) ds

S(E) =h log(1 + aE)

f Eg + bEd + cEe

Transferred energy

electronic interaction

Fit to stopping power

electrons interaction

Effective temperature

after energy

transfer

Dissociation probability

22

E = 5 MeV/nuc. - 10 GeV ➞ Electronic interaction only

Stopping of high-energy ions

S =⇤Z2�2

Z21

( f(�) � C

Z2� lnhIi � ⇥

2

�

+Z1 L1( Barkas ) + Z21 L2 ( Bloch )

)Stopping

power

Shell

correction

Mean

ionisation

Density

effect� ⌘ 4⇥ r20 mec2

Ziegler et al. 1999

Bethe - Bloch equation

23

Photo-dissociation rate

vs.

Following Vis-UV absorption

24

Photo-absorption cross section IIOptical - UV

Li, A. & Draine, B. T. 2001, ApJ, 554, 778 Jones, A. P. 2012, A&A, 542, A98

25

Photon absorption rateOptical - UV

vs.

26

Modified size distributions IThe effect of photo-dissociation

Power-law for all:

the “native” distribution of

nanoparticles - J12

Log-normal for all:

the “native” distribution of astronomical PAHs - LD01

27

Photo-absorption cross section IIIInfrared

Verstraete, L. & Léger, A. 1992, A&A, 266, 513 — Compiègne, M., et al. 2011, A&A, 525, A103 Li, A. & Draine, B. T. 2001, ApJ, 554, 778 — Draine, B. T. & Li, A. 2007, ApJ, 657, 810 Jones, A. P. 2012, A&A, 542, A98