1. VIBRATIONAL SPECTROSCOPY OF GERMANIUM-CARBON CLUSTERS: ν4(σu) MODE OF GeC5Ge
E. Gonzalez, C.M.L. Rittby, and W.R.M. Graham
Texas Christian University
Molecular Physics Laboratory

2. Motivation The Group IVB molecular clusters, SinCm, GenCm, and
SinCmGel, are of experimental and theoretical interest
because of their novel structures and potential applications
in semiconductor technology and microelectronics
products (J. Karolczak,J. Chem. Phys. (1995), O. Leifeld, Nano. (1999).,
O. Leifeld, Appl. Phys. Lett. (1999). ,R. Hartmann, Appl. Phys. Lett. (1998).) .
Previously, we have reported vibrational spectra for
SinCm (X.D. Ding, J. Chem, Phys. (1999) ) , GenCm , and SinCmGel
(D.L. Robbins, J. Chem. Phys. (2001,2002,2004). ) clusters. Could we
form new species?

3. Objectives To form novel germanium-carbon clusters by dual-laser
ablation of germanium and carbon rods.
Identify structure via isotopic shift measurements and
assign the vibrational fundamentals

4. Dual Laser Ablation Setup
laser focusing lenses
Nd-YAG
1064 nm pulsed lasers, 1.0 to 3.0 Watts
Gold mirror held
held at ~10 K
Quartz window
FTIR
(MCT detector)
~10-8Torr
CsI window
Germanium
Carbon
Ar flow

5. Strategy To identify structure:
To measure frequencies and intensities of isotopomers
formed by evaporating carbon rods with a 13C enrichment.
In order to limit the complexity of the isotopic spectrum
two experiments are carried out with different carbon rods
having low (5-30%) and high (70-95%) 13C enrichment
respectively. The first one to obtain single and double
13C substitutions, the second to obtain 12C substitutions.

6. Strategy (cont.) DFT Calculations:
To perform DFT calculations of geometries linked with the
obtained spectra.
Isotopic shift calculation and simulated spectra with the experimental
13C enrichment are generated to sustain the identified structure and
vibrational assignment.

7. Carbon Rods Homemade carbon rods with the desired ratio of 13C:12C
by mass weight.
Isotopomers probability of Cn bearing species:
: Number of 13C isotopic substitutions
: Number of carbon atoms
: 13C concentration 12 13

8. Example: C5 bearing species
Single substitutions
Example: C5 bearing species
Double substitutions
Triple substitutions
Quadruple substitutions
Probability
0.1
Low 13C
High 13C
0.08
0.06
0.04
0.02 20 40 60 80
100
13C Concentration

9. C5
90% 12C / 10% 13C
10% 12C / 90% 13C
2130
2140
2150
2160
2080
2090
2100
2110
2120
Absorbance
12C12,v7
Frequency (cm-1)

10. (a) 12C rod + Ge rod (b) 12C rod C9 n6 GeC9 n4 GeC3Ge n3 GenCm C6 n5
1998.0 n6
GeC9 n4
1928.3
(a) 12C rod + Ge rod
GeC3Ge n3
GenCm C6
1952.5 n5
GeC7 n1
2063.8
2093.2
GenCm
1920.3
2158.0
1936.7 Cn C7 n4
2127.8 C5 n3
2164.1 n9 n3 n7
C12 n5 C3
C11 n7 n8 C7
1894.3
1818.0
C10
1946.1
2038.9
C11
Absorbance
1915.8
1856.7
(b) 12C rod
1750
1800
1850
1900
1950
2000
2050
2100
2150

11. (a) Ge rod and 15% 13C rod C7 C5 Cn 2100 2110 2120 2130 2140 2150 2160
C5 single substitutions
C5 double substitutions C7
(A) C5
2127.9
2158.0
2164.1
C12
2140.0
(B)
(C),(F)
(G)
(D),(H)
(I) Cn
2155.1
(J)
Absorbance
(E)
2116.3
2116.8
2138.2
2142.3
2123.4
2105.2
2154.2
Frequency (cm-1)
2100
2110
2120
2130
2140
2150
2160
2170

12. (a) Ge rod and 85% 13C rod C5 C5 single substitutions
2080.4
(A')
C5 single substitutions
C5 double substitutions
2074.7
2077.8
(B' )
(C' ),(F' )
(H' )
(I' )
(D')
2098.8
2114.4
2116.6
2120.2
Absorbance
Frequency (cm-1)
2070
2080
2090
2100
2110
2120
2130
2140
2150

13. DFT Calculations We did DFT calculations for GeC5Ge because:
It is consistent with the shown isotopic spectra.
Previous experimental measurements and DFT calculations have shown that the original linear carbon chain structure is retained on the addition of a Si and Ge atom to one or both end. For example, SiC3Si, SiC4, SiC4Si, GeC3Ge, GeC7, GeC9, GeC3Si.

14. DFT predicted (B3LYP/cc-pVDZ) ground state geometry for GeC5Ge cluster
1.2918
1.2897
1.7897 Å
1.2897
1.2918 Ge

15. DFT B3LYP/cc-pVDZ predicted vibrational frequencies (cm-1) and band intensities for the linear GeC5Ge
2158.0
2163.9
2140
2160
2180
calculated
4592
km/mol
2539
GeC5Ge C5

16. Statistical Analysis Molecule Exp. Frq. Theo. Frq Ratio
y = x R 2
= 0.969
1000.0
1200.0
1400.0
1600.0
1800.0
2000.0
2200.0
2400.0
1500.0
2500.0
Theoretical Frequencies (cm-1)
Experimetal Frequencies (cm-1)

17. Expected Experimental Frequency: (using linear regression)
Statistical Analysis
Molecule Exp. Frq. Theo. Frq Ratio
Theoretical Frequency: cm-1
Expected Experimental Frequency:
(2054 ± 133) cm-1
(using linear regression) ]
2187 cm-1 [
1921 cm-1
2158 cm-1!

18. Comparison of observed vibrational frequencies (cm-1) of the 4(σu) mode for 13C- substituted isotopomers of linear GeC5Ge with the predictions of B3LYP/cc-pVDZ level calculations.
aResults of the DFT-B3LYP/cc-pVDZ calculation scaled by a factor of /2135.0=
 bOverlapped by band C.  cOverlapped by band D.

19. (a) Ge rod and 15% 13C rod (b) DFT simulation 15% 13C 2100 2110 2120
2123.4
2127.9
2155.1
2158.0
2164.1
Frequency (cm-1)
Absorbance
(a) Ge rod and 15% 13C rod
(b) DFT simulation 15% 13C C7 C5
(A)
(B)
2142.3
(E)
2154.2
2138.2
2140.0
C12
2105.2
(J)
2116.8
2116.3
(C),(F)
(G)
(D),(H)
(I)
C5 single substitutions
C5 double substitutions Cn
2100
2110
2120
2130
2140
2150
2160
2170
(D)
(H)

20. Comparison of observed vibrational frequencies (cm-1) of the 4(σu) mode for 12C- substituted isotopomers of linear GeC5Ge with the predictions of B3LYP/cc-pVDZ level calculations.
aResults of the DFT-B3LYP/ cc-pVDZ calculation scaled by a factor of /2051.0=
bOverlapped by 3(σu) mode of 13C cOverlapped by C5 double-12C isotopomer shift.

21. (a) Ge rod and 85% 13C rod (b) DFT simulation 85% 13C
Frequency (cm-1)
Absorbance
(a) Ge rod and 85% 13C rod
(b) DFT simulation 85% 13C
2070
2080
2090
2100
2110
2120
2130
2140
2150
2077.8
(B´)
2074.7
2080.4 C5
(A´)
C5 single substitutions
C5 double substitutions
2098.8
(C´),(F´)
2114.4
2120.2
(H´)
(I´)
(D´)
2116.6
(J´)
(E´)
(G´)

22. Conclusion
The linear GeC5Ge germanium-carbon chain has been detected for the first time through the dual laser evaporation of graphite and germanium.
FTIR isotopic shift measurements and DFT calculations at the B3LYP/cc-pVDZ level confirm the identification of the ν4(σu) vibrational fundamental at cm-1 .

23. ACKNOWLEDGMENTS The Welch Foundation
The Welch Foundation
TCU Research and Creative Activities Fund
The W.M. Keck Foundation

24. References(1)

25. References(2)