VIBRATIONAL SPECTROSCOPY OF GERMANIUM-CARBON CLUSTERS:

ν4(σu) MODE OF GeC5Ge

E. Gonzalez, C.M.L. Rittby, and W.R.M. GrahamTexas Christian University

Molecular Physics Laboratory

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?

Objectives

•To form novel germanium-carbon clusters by dual-laserablation of germanium and carbon rods.

•Identify structure via isotopic shift measurements andassign the vibrational fundamentals

Quartz window

laser focusing lenses

Carbon

Dual Laser Ablation Setup

Ar flow

Nd-YAG1064 nm pulsed lasers, 1.0 to 3.0 Watts

Germanium

FTIR (MCT detector)

~10-8Torr

CsI window

Gold mirror held held at ~10 K

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 enrichmentrespectively. The first one to obtain single and double 13C substitutions, the second to obtain 12C substitutions.

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.

Carbon Rods

Homemade carbon rods with the desired ratio of 13C:12Cby mass weight.

12 12

12

12

1212

12

13

13

13

Isotopomers probability of Cn bearing species:

,

100

100 100

n q q

n q

a ap

: Number of 13C isotopic substitutionsn: Number of carbon atomsq: 13C concentrationa

High 13CLow 13C

0.1Probability

20 40 60 80 10013C Concentration

0.02

0.04

0.06

0.08

Single substitutionsDouble substitutionsTriple substitutionsQuadruple substitutions

Example: C5 bearing species

C5

10% 12C / 90% 13C12-12-12-12-12

12-13-12-12-12

13-12-12-12-12

12-12-13-12-1212C12,v7

2130 2140 2150 2160 2080 2090 2100 2110 2120

13-13-13-13-13

12-13-13-13-13

13-12-13-13-13

13-13-12-13-13

Frequency (cm-1)

Abs

orba

nce

90% 12C / 10% 13C

GeC9

4

192

8.3

193

6.7

Cn

C6

195

2.5

5

C718

94.

3

GeC3Ge3

C12

C11C10

C11C3

Ab

sorb

ance

(a) 12C rod + Ge rod

(b) 12C rod

C5

3

216

4.1

C7

4

212

7.8

GeC7

1

206

3.8

203

8.9

3

194

6.1

7

191

5.8

7

5

185

6.7

8

9

181

8.0

1750 1800 1850 1900 1950 2000 2050 2100 2150

215

8.0

209

3.2

GenCm

192

0.3 GenCm

C9

199

8.0

6

2123

.421

27.9

2155

.1

2158

.0

2164

.1

Ab

sorb

ance

(a) Ge rod and 15% 13C rod

C7 C5(A)

(B)

2142

.3

(E)

2154

.22138

.221

40.0

C12

2105

.2

(J)

2116

.821

16.3

(C),(F)(G)(D),(H)(I)

C5 single substitutionsC5 double substitutions

Cn

Frequency (cm-1) 2100 2110 2120 2130 2140 2150 2160 2170

2074

.7

2080

.4

Ab

sorb

ance

(a) Ge rod and 85% 13C rodC5

(A') C5 single substitutionsC5 double substitutions

2077

.8

(B' )

2098

.8

(C' ),(F' )

2114

.4

2120

.2

(H' ) (I' )(D')

2116

.6

Frequency (cm-1) 2070 2080 2090 2100 2110 2120 2130 2140 2150

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.

1.7897 Å 1.2897 1.2918

1.2918 1.2897 1.7897 Ge

Ge

DFT predicted (B3LYP/cc-pVDZ) ground state geometry for GeC5Ge cluster

DFT B3LYP/cc-pVDZ predicted vibrational frequencies (cm-1) and band intensities for

the linear GeC5GeVibration

al mode

Frequency (cm-1)

Infrared intensity (km/mol)

ν1(σg) 2027.0 0

ν2(σg) 1075.3 0

ν3(σg) 240.8 0

ν4(σu) 2135.0 4592

ν5(σu) 1619.2 1212

ν6(σu) 561.9 148

ν7(πg) 516.3 0

ν8(πg) 121.5 0

ν9(πu) 628.7 13

ν10(πu) 237.8 7

ν11(πu) 43.3 1

2158

.0

2163

.9

2140 2160 2180

calculated4592 km/mol

calculated2539 km/mol

GeC5GeC5

Statistical Analysis

y = 0.9557x + 13.661

R2 = 0.969

1000.0

1200.0

1400.0

1600.0

1800.0

2000.0

2200.0

2400.0

1000.0 1500.0 2000.0 2500.0

Theoretical Frequencies (cm-1)

Exp

erim

etal

Fre

qu

enci

es (

cm-1)

Molecule Exp. Frq. Theo. Frq Ratio Molecule Exp. Frq. Theo. Frq Ratio

C3 2038.9 2157.8 0.945C4 1543.4 1597.6 0.966C5 1446.6 1498.8 0.965C5 2164.1 2269.7 0.953C6 1197.3 1233.3 0.971C6 1952.5 2037.8 0.958C7 1894.3 1988.5 0.953C7 2127.8 2258.4 0.942C8 1710.5 1770.2 0.966C8 2071.7 2168.2 0.955C9 1600.9 1671.3 0.958C9 1998.0 2132.4 0.937C9 2078.1 2217.5 0.937C10 1915.8 1997.4 0.959C10 2074.9 2196.6 0.945C11 1856.7 1946.9 0.954

C11 1946.1 2126.2 0.915C12 1818.0 1816.5 1.001C12 1997.3 2112.8 0.945C12 2140.6 2188.2 0.978GeC3Ge 1920.7 2064.0 0.931GeC7 2063.6 2131.9 0.968GeC9 1928.3 1934.9 0.997GeC4 2093.3 2181.8 0.959SiC7 2100.8 2134.3 0.984SiC9 1935.8 1936.9 0.999SiC2 1741.3 1837.5 0.948SiC4 2080.1 2196.4 0.947Si2C2 1188.4 1303.4 0.912Si2C3 1955.2 2061.1 0.949Si2C4 1807.4 1859.1 0.972GeC5Ge 2158.0 2135.0 1.011

Statistical AnalysisMolecule Exp. Frq. Theo. Frq Ratio

C11 1946.1 2126.2 0.915C12 1818.0 1816.5 1.001C12 1997.3 2112.8 0.945C12 2140.6 2188.2 0.978GeC3Ge 1920.7 2064.0 0.931GeC7 2063.6 2131.9 0.968GeC9 1928.3 1934.9 0.997GeC4 2093.3 2181.8 0.959SiC7 2100.8 2134.3 0.984SiC9 1935.8 1936.9 0.999SiC2 1741.3 1837.5 0.948SiC4 2080.1 2196.4 0.947Si2C2 1188.4 1303.4 0.912Si2C3 1955.2 2061.1 0.949Si2C4 1807.4 1859.1 0.972GeC5Ge 2158.0 2135.0 1.011

Theoretical Frequency: 2135.0 cm-1

Expected Experimental Frequency:

(2054 ± 133) cm-1

(using linear regression)

]2187 cm-1

[1921 cm-1

2158 cm-1!

Isotopomer Observed B3LYP/

cc-pVDZ Scaleda

Difference

Ge-C-C-C-C-C-Ge

ν ν ν Δν

74-12-12-12-12-12-74 (A) 2158.0 2135.0 2158.0 …

74-13-12-12-12-12-74 (B) 2155.1 2133.6 2156.6 1.5

74-12-13-12-12-12-74 (C) 2142.3 2119.5 2142.3 0.0

74-12-12-13-12-12-74 (D) 2116.8 2096.3 2118.9 2.1

74-13-12-12-12-13-74 (E) 2154.2 2132.0 2154.9 0.7

74-13-13-12-12-12-74 (F) ---b 2119.3 2142.1 ---

74-13-12-12-13-12-74 (G) 2138.2 2116.5 2139.2 1.0

74-12-13-12-13-12-74 (H) ---c 2095.5 2118.0 ---

74-13-12-13-12-12-74 (I) 2116.3 2094.4 2117.0 0.7

74-12-13-13-12-12-74 (J) 2105.2 2082.1 2104.4 -0.8

Comparison of observed vibrational frequencies (cm-1) of the 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 2158.0/2135.0=1.01076. bOverlapped by band C.  cOverlapped by band D.

2123

.4

2127

.9

2155

.1

2158

.0

2164

.1

Frequency (cm-1)

Ab

sorb

ance

(a) Ge rod and 15% 13C rod

(b) DFT simulation 15% 13C

C7

C5

(A)

(B)

2142

.3

(E)

2154

.22138

.221

40.0

C1221

05.2

(J)21

16.8

2116

.3(C),(F)(G)(D),(H)(I)

C5 single substitutionsC5 double substitutions

Cn

2100 2110 2120 2130 2140 2150 2160 2170

(B)(C),(F)

(D)(H)

(E)(G)(I)(J)

Isotopomer Observed B3LYP/

cc-pVDZ Scaleda

Difference

Ge-C-C-C-C-C-Ge

ν ν ν Δν

74-13-13-13-13-13-74 (A') 2074.7 2051.0 2074.7 ---

74-12-13-13-13-13-74 (B') 2077.8 2053.0 2076.8 -1.0

74-13-12-13-13-13-74 (C') 2098.8 2076.9 2101.0 2.2

74-13-13-12-13-13-74 (D') 2116.6 2093.0 2117.2 0.6

74-12-13-13-13-12-74 (E') ---b 2054.6 2078.3 ---

74-12-13-13-12-13-74 (F') 2098.8 2077.2 2101.2 2.4

74-12-12-13-13-13-74 (G') ---c 2081.9 2106.0 ---

74-13-12-13-12-13-74 (H') 2114.4 2092.1 2116.3 1.9

74-12-13-12-13-13-74 (I') 2120.2 2094.3 2118.5 -1.7

74-13-12-12-13-13-74 (J') --- 2116.1 2140.6 ---

Comparison of observed vibrational frequencies (cm-1) of the 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 2074.7/2051.0=1.0116.bOverlapped by 3(σu) mode of 13C5. cOverlapped by C5 double-12C isotopomer shift.

Frequency (cm-1)

Ab

sorb

ance

(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 substitutionsC5 double substitutions

2098

.8

(C´),(F´)

2114

.4

2120

.2

(H´) (I´)(D´)

2116

.6(J´)(E´) (G´) (H´) (I´)

(D´)

(B´) (C´),(F´)

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 2158.0 cm-1 .

ACKNOWLEDGMENTS 

•The Welch Foundation •TCU Research and Creative Activities

Fund •The W.M. Keck Foundation

References(1)1 J. Karolczak, W.W. Harper, R.S. Grev, and D. J. Clouthier, J. Chem. Phys. 103, 2840 (1995). 2 O. Leifeld, R. Hartmann, E. Miller, E. Kaxiras, K. Kern, and D. Gritzmacher, Nano. 10, 122 (1999). 3 O. Leifeld, R. Hartmann, E. Miller, E. Kaxiras, K. Kern, and D. Gritzmacher, Appl. Phys. Lett. 74, 994 (1999). 4 R. Hartmann, U. Gennser, H. Sigg, K. Ensslin, and D. Gritzmacher, Appl. Phys. Lett. 73, 1257 (1998). 5 X.D. Ding, S.L. Wang, W.R.M. Graham, and C.M.L. Rittby, J. Chem, Phys. 110, 11214 (1999), and references cited therein. 6 D.L. Robbins, C.M.L. Rittby, and W.R.M. Graham, J. Chem. Phys. 114, 3570 (2001). 7 D.L. Robbins, C.M.L. Rittby, and W.R.M. Graham, J. Chem. Phys. 120, 4664 (2004). 8 D.L. Robbins, C.M.L. Rittby, and W.R.M. Graham, J. Chem. Phys. 117, 3811 (2002). 9 J.D. Presilla-Márquez and W.R.M. Graham, J. Chem. Phys. 100, 181 (1994); C.M.L. Rittby, ibid., 100, 175 (1994). 10 J.D. Presilla-Márquez, S.C. Gay, C.M.L. Rittby, and W.R.M. Graham, J. Chem. Phys. 102, 6354 (1995). 11 J.D. Presilla-Márquez, C.M.L. Rittby, and W.R.M. Graham, J. Chem. Phys. 104, 2818 (1996).

12 X.D. Ding, S.L. Wang, W.R.M. Graham, and C.M.L. Rittby, J. Phys. Chem. A 104, 3712 (2000). 13 R.E. Kinzer, C.M.L. Rittby, and W.R.M. Graham, J. Chem. Phys., submitted (2006). 14 S.L. Wang, C.M.L. Rittby, and W.R.M. Graham, J. Chem. Phys. 107, 6032 (1997).

References(2)15 S.L. Wang, C.M.L. Rittby, and W.R.M. Graham, J. Chem. Phys. 107, 6032 (1997). 16 S.L. Wang, C.M.L. Rittby, and W.R. M. Graham, J. Chem. Phys. 107, 7025 (1997); ibid., 112, 1457 (2000), 17 P.A. Withey and W.R.M. Graham, J. Chem. Phys. 96, 4068 (1992). 18 J.D. Presilla-Márquez, C.M.L. Rittby, and W.R.M. Graham, J. Chem. Phys. 106, 8367 (1997). 19 Gaussian 03, Revision A.1, M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, J. A. Montgomery, Jr., T. Vreven, K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratchian, J. B. Cross, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, P. Y. Ayala, K. Morokuma, G. A. Voth, P. Salvador, J. J. Dannenberg, V. G. Zakrzewski, S. Dapprich, A. D. Daniels, M. C. Strain, O. Farkas, D. K. Malick, A. D. Rabuck, K. Raghavachari, J. B. Foresman, J. V. Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J. Cioslowski, B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. L. Martin, D. J. Fox, T. Keith, M. A. Al-Laham, C. Y. Peng, A. Nanayakkara, M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen, M. W. Wong, C. Gonzalez, and J. A. Pople, Gaussian, Inc., Pittsburgh PA, 2003. 20 L.N. Shen, T.J. Doyle, and W.R.M. Graham, J. Phys. Chem. 93, 1597 (1990). 21 X.D. Ding, S.L. Wang, C.M.L. Rittby, and W.R.M. Graham, J. Chem. Phys. 112, 5113 (2000). 22 R.H. Kranze and W.R.M. Graham, J. Chem. Phys. 96, 2517 (1992). 23 R.H. Kranze, C.M.L. Rittby, and W.R.M. Graham, J. Chem. Phys. 105, 5313 (1996).