investigation of carbonaceous interstellar dust...

Belén Maté,Miguel Jiménez-Redondo, Isabel Tanarro, Miguel Moreno, and

Victor HerreroInstituto de Estructura de la Materia (IEM-CSIC), Serrano 123, 28006,

Madrid, Spain

[email protected]

ISMS - 70TH MEETING - JUNE 22-26, 2015 - CHAMPAIGN-URBANA, ILLINOIS

Investigation of carbonaceous interstellar dust analogues by infrared spectroscopy:

Effects of energetic processing

Funding: CDS2009-00038, FIS20012 -38175, FIS2013-48087-C2-1-P, ERC-2013-Syg 610256

INSTITUTO DE ESTRUCTURA DE LA MATERIA


Interstellar hydrocarbon dust

IR absorptionfeatures

3.4 m bandJ. Chiar et al. ApJ 2013, 770, 78A. P. Jones ASP Conf. Ser. 414, 2009

Carbonaceous dust in the diffuse ISM

E. Dartois et al. A&A, 2007, 463, 635

Hydrogenated amorphous carbon (HAC or a-C:H) produced in the laboratory

CH aromatic

(upper limit)

CCaromatic

+ olefinic

CH Aliphaticstretchings

CHaliphaticbendings

Structure estimates by Dartois et al. suggest an important contribution of

hydrogen rich aliphatic carbon

Aliphatic features are more prominent

their absorption strengths are much higher

Amorphous C/H ternary diagram

PAHs

E. Dartois et al. A&A, 2007, 463, 635

Carbonaceous dust in the diffuse ISM

J. Chiar et al. ApJ , 2013, 770, 78

Left: weighted average of the spectra of the six quintuplet lines of sight. Right: ISO spectra

UKIRT spectra toward the Galactic center Quintuplet Cluster

Structure estimates by Chiar et al.suggest that the dust is hydrogen poor

and highly aromatic

HAC film deposition in CH4/He plasmaIEM-CSIC

• CH4(40%)/He 0.3 mbar

• 40 W , 13.56 MHz

outside the coilHAC1

inside the coilHAC2

Inductively coupled RF discharge reactor

Film thickness ~ 3 µm

1 hour

IR spectra of the deposits

3000 2500 2000 1500 1000

0,0

0,1

0,2

0,3

0,4

0,5

ab

sorb

ance

wavenumber / cm-1

CH stretch C=Cstretch

CHx bend

AromaticsAliphatics

Outside the coil

Inside the coil x5

6.9 µm6.2 µm

11.3 µm

CH3 CH3CH2

7.2 µmCH3

CH2

CH3

3.4 µm

B. Maté et al. Faraday Disc. 2014, 168, 267

HAC 1

HAC 2

Analysis of HAC spectra

H 0.33

sp2 0.55

sp3 0.11

3200 3000 2800 1800 1700 1600 1500 1400 1300

0,00

0,05

0,10

0,15

0,20

0,25

Math X1

0,0

0,1

0,2

0,3

0,4

Abs

orba

nce

3200 3800 2800 1700 1500 1300Wavelength/ cm-1

0.4

0.2

0.2

0.1

Abso

rban

ceCH2, CH3sp3

CCsp2

CHsp2

HAC 1

HAC 2H 0.13

sp2 0.83

sp3 0.04

Using absorption strengths from Chiar et al. ApJ 2013, 770, 78

CO?

HAC2HAC1

3,2 3,3 3,4 3,5 3,6

-0,20

-0,15

-0,10

-0,05

0,00

5,5 6,0 6,5 7,0 7,5

3,2 3,3 3,4 3,5 3,6

-0,8

-0,4

0,0

5,6 5,8 6,0 6,2 6,4 6,6

Comparison with observations in the diffuse ISM

Infrared Galaxy IRAS 08572+3915Dartois et al. A&A 2007

Galactic center Quintuplet Cluster.Chiar et al. ApJ, 2013,

Opt

ical

dep

th

Wavelength µm

3,2 3,3 3,4 3,5 3,6

-0,20

-0,15

-0,10

-0,05

0,00

5,5 6,0 6,5 7,0 7,5

3,2 3,3 3,4 3,5 3,6

-0,8

-0,4

0,0

5,6 5,8 6,0 6,2 6,4 6,6




Opt

ical

dep

th

Wavelength µm

HAC 1 spectrum scaled to the maximum

3,2 3,3 3,4 3,5 3,6

-0,20

-0,15

-0,10

-0,05

0,00

5,5 6,0 6,5 7,0 7,5

3,2 3,3 3,4 3,5 3,6

-0,8

-0,4

0,0

5,6 5,8 6,0 6,2 6,4 6,6




Opt

ical

dep

th

Wavelength µm



3000 2000 1000

0.00

0.01

0.02

0.03

abso

rban

ce

wavenumber cm-1

Deposit growth and structure

3000 2900 2800

0.00

0.01

0.02

0.03

abso

rban

ce

wavenumber cm-1

The H/C and sp3/sp2 ratios decrease with growing thickness

Inside the coil

3 min ~ 100 nm6 min ~ 200 nm12 min ~ 400 nm

H2 plasma 0.25 mbar, 40 W

0 min 4 min

10 min

Processing in H2 plasma

The CC stretch band remainsunchanged

CC bonds polyaromatic ratherthan olefinic

The CHx stretch band decreases with

processing

CC

Summary and conclusions

• Carbonaceous dust analogues have been grown in inductively coupled RF discharges of He+CH4.

• The position in the plasma reactor affects the structure of the deposited hydrocarbon. Inside coil deposits are good

analogues to interstellar medium dust.

• Processing with H2 plasma do not affect the aromatic component of the carbonaceous material.

Belén Maté, [email protected] DE ESTRUCTURA DE LA MATERIA


investigation of carbonaceous interstellar dust...

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