Systematics in the IR

Absorptionsof Odd Carbon

Chains

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21st of June 2005, Columbus

Dmitry Strelnikov, Roman Reusch and Wolfgang Krätschmer Max-Planck-Institut für Kernphysik, Heidelberg, Germany

Experimental Setup

V

+

-

S te p m o to r

D C P o w e rS u p p ly

W ate rco o lin g

T u rb o M o le cu la r p u m p s

U V- (O M A ) a n dF T IR - (M C T ) sp e c tro m e te rd e te c to rs

Va lv e

C ry o g en ic p u m p

7 -4 0 K M a trix

M a trix g a s in le t(A r, N e , O 2 e tc .)

IR -lig h t so u rc eU V-lig h tso u rc e

P u lse d E X C IM E R -D Y E L A S E R

R ad ia tio n sh ie ld

Io n so u rce

Q u ad ru p o le M ass A n a ly z e r

Io n d e tec to r

C a rb o n v a p o r m o lecu le s

G rap h itero d s

Matrix-isolated carbon molecules

Carbon vapor molecules as depositedin cryogenic Ne-, Ar- or Kr-matrices

Chain growth by matrixannealing

UV/Vis-spectra before and after annealing in Ar

20002010202020302040W avenum ber cm -1

T=35K

T=11K

C 9

C 3 IR-spectra before andafter annealing in Ar

300 350 400 450 500

W avelength, nm

C 11

C 9C 15

C 13C 17

C 3

Strategy

□ Comparison of IR and UV/Vis absorptions of Cn in Ar and O2 matrices

□ Method´s test: Selective oxidation of Cn with known IR and UV/Vis absorption spectra

□ Method´s application: Selective oxidation of Cn

with unknown IR but known UV/Vis absorptions□ Looking for systematics in the IR spectra of long

C2n+1 molecules

C 15

C 13

C 11

C 9

C 17

C n in O 2, 25K

C 6

C 9 C 11

C 13C 15

C 17

C n in A r, 32KD.Forney, P.Freivogel, M.Grutter and J.P.Maier, J. Chem. Phys., 1996

250 300 350 400 450 500W avelength, nm

Cn absorbtions in Ar matrix, UV-vis spectrumCn absorbtions in Ar and O2 matrices, UV-vis spectrum

16001700180019002000W avenum ber, cm

-1

C 9

C 6 C 11

C 11C 9

C 10

C 13

C 9

C n in O 2, 25K

C 3

C 9

C 6

C 7C 11

C 11C 10

C 3C 9

cyc-C 6

C 10C 8

C 8C 9

C n in A r, 32K

C 13

A. Van Orden and R. Saykally; Chem. Rev. 1998

Cn absorbtions in Ar and O2 matrices, IR spectrumCn absorbtions in O2 matrix, IR spectrumCn absorbtions in Ar matrix, IR spectrum

1700175018001850

W avenum ber cm-1

C n in 16O 2 m atrix

C n in 18O 2 m atrix

Isotopic substitution of matrix oxygen. The way to distinguish pure carbon molecules and oxides.

□ Comparison of IR and UV/Vis absorptions of Cn in Ar and O2 matrices

□ Method´s test: Selective oxidation of Cn with known IR and UV/Vis absorption spectra

□ Method´s application: Selective oxidation of Cn

with unknown IR but known UV/Vis absorptions□ Looking for systematics in the IR spectra of long

C2n+1 molecules

Selective LASER-induced oxidation of carbon chains in O2-matrices.

LASER

300 350 400 450

W avelength nm

C 9

LASER @ 308 nm

C 11

C 13

C 15

Difference in absorption before and after LASER exposure

UV-vis IR

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W avenum ber cm -1

O xide

O xide

C 9

Flash Movie

1500160017001800190020002100220023002400W avenum ber, cm

-1

Photo bleaching of C 9 in oxygen matrix, IR spectrum.

C 9

C 9C 9

C 6

C O 2

C 3O

C 11

C 11

Before irrad ia tion

A fter irrad ia tion

D ifference

C 5O 2C O

C O 3C 6O 2*

20 m in of laser irrad iation at 308 nm . Tem perature of m atrix 24K .

* O ur identification

□ Comparison of IR and UV/Vis absorptions of Cn in Ar and O2 matrices

□ Method´s test: Selective oxidation of C9, C11, C13

having known IR and UV/Vis absorption spectra

□ Method´s application: Selective oxidation of Cn

with unknown IR but known UV/Vis absorptions□ Looking for systematics in the IR spectra of long

C2n+1 molecules

250 300 350 400 450 500W avelength, nm

Photo bleaching of C 15 in oxygen matrix, UV-vis spectrum.

C 15C 13

Before irrad iation

After irrad iation

D ifference

80 m in of laser irrad ia tion at 438-454 nm . Tem perature of m atrix 24K .

LASER

1500160017001800190020002100220023002400W avenum ber, cm

-1

C O 2

C 3O

C 15

C 11C 11

C 9

Photo bleaching of C 15 in oxygen matrix, IR spectrum.

Before irrad ia tion

A fter irrad ia tion

D ifference

C 5O 2

C 6O 2*

C O

C O 3

80 m in of laser irradiation at 438-454 nm . Tem perature of m atrix 24K .

* O ur identification

1680169017001710172017301740

W avenum ber cm-1

240 m in of laser irrad iation at 443-453 nm ,Ar+10% O 2-m atrix, 25K .

C 15

C 15

C 15

Before irrad iation

A fter irrad iation

350 400 450 500 550 600

W avelength, nm

LASER

Photo bleaching of C 21 in oxygen matrix, UV-vis spectrum.

60 m in of laser irrad ia tion at 585-590 nm .

Tem perature of m atrix 25K .C 15

C 17

C 19C 21

Before irrad iation

A fter irrad iation

D ifference

1000110012001300140015001600

W avenum bers, cm-1

C 9

C 21

O 3Before irrad ia tion

A fter irrad ia tion

D ifference

Photo bleaching of C 21 in oxygen matrix, IR spectrum.

60 m in of laser irrad iation at 580-595 nm . Tem perature of m atrix 25K .

□ Comparison of IR and UV/Vis absorptions of Cn in Ar and O2 matrices

□ Method´s test: Selective oxidation of Cn with known IR and UV/Vis absorption spectra

□ Method´s application: Selective oxidation of Cn

with unknown IR but known UV/Vis absorptions□ Looking for systematics in the IR spectra of long

C2n+1 molecules

13001400150016001700180019002000W avenum ber cm

-1

C 9

C 13

C 15

C 11

C 11

C 17C 19

C 21

??

IR-absorptions of carbon molecules in Ar, 30K

Where are the (3N-5)/2

IR-active modes ?

...+ + + +- - -

N

ikii

N

i k

i

i

N

k

Skredk

Lqs

x

x

xx

ds

d

ds

d

mI

1,

1

1

2

0

),,(

1~

xLs 1

PM3, DFT(b3lyp/6-311G(d))

- intensity of the k-th vibrational mode

- dipole moment,xk, sk - Cartesian and normal coordinates,qi - Mulliken charges,Li,k – matrix of vibrational eigenvectors as columns ( )

Intensities of infrared absorptions of long odd-numbered carbon chain molecules

120013001400150016001700180019002000

Wavenum ber cm -1

C n in A r, 32KC n in N e, 8K

C 9

C 11 C 13

C 15

C 17

C 19

C 21

C 11

Red and blue Ne-to-Ar (gas-to-Ar) matrix-shifts of the totally alternating vibration for

long odd-numbered carbon chains

Cn in gas phase

* * *

* - Prediction

Conclusion

The method of selective laser-induced oxidation works and turned out to be useful for the characterization of odd linear carbon chains.

A regularity in the IR-absorptions of linear C2n+1 species was established.