Vanadium and ChromiumCarbon Cluster Studies

1
Infrared Observation of the ?1(?) and ?2(?)
Stretching Modes of Linear GeC3
E. Gonzalez, C.M.L. Rittby, and W.R.M. Graham
Department of Physics and Astronomy Texas
Christian University Fort Worth, TX 76129 63rd
Meeting of the International Symposium on
Molecular Spectroscopy The Ohio State
University June 16-20, 2008
2
Motivation

• Form novel germanium-carbon clusters by single
  laser ablation of germanium-carbon sintered rods.
  
• Target GeC3 molecule that had not been observed
  when GeC3Ge and GeC3Si were discovered
• (Robbins et al, JCP. 2001,2002)
• Identify structure via isotopic shift
  measurements and assign the vibrational
  fundamentals

3
Experimental Setup
laser focusing lens
Nd-YAG 1064 nm pulsed laser, 0.2 to 3.0 Watts
Gold mirror held held at 10 K
Quartz window
FTIR (MCT detector)
10-8Torr

CsI window
Ge/C/Si sintered rod
See MJ06 for an animated schematic of the dual
ablation set up
Ar flow
4
Previous Work

• Germanium carbon clusters
• Linear GeC3Ge was previously produced by dual
  laser ablation of germanium and carbon rods. The
  ?3(?u) fundamental was assigned at 1920.7 cm-1
• (D.L. Robbins et al, J. Chem. Phys. 2001 )
• Small germanium-carbon clusters have been
  investigated by Leszczynski et al. using DFT,
  MP2, CCSD, and CCSD(T) levels of theory
• (Leszczynski et. al. J. Chem. Phys. 2005)

5
Previous Work

• In later work using single laser ablation of a
  sintered germanium-carbon rod the yield of GeC3Ge
  was improved allowing the observation of the next
  most intense infrared active modes
• The ?4(?u) stretching mode was assigned to 735.3
  cm-1 (74-12-12-12-74) and the bending mode ?6(pu)
  was assigned to 580.1cm-1 (to be published)

6
The ?4(?u) stretching mode of linear
GeC3Ge (to be published)
736.0 74-12-12-12-72
735.3 74-12-12-12-74 76-12-12-12-72
736.7 74-12-12-12-70 72-12-12-12-72
737.5 72-12-12-12-70,
734.5 76-12-12-12-74
738.3 70-12-12-12-70,
Ge/12C rod
Simulation
720
725
730
735
740
745
750
Frequency (cm-1)
7
Previous Work

• Germanium, carbon, and silicon mixed cluster
• Linear GeC3Si was previously produced by dual
  laser ablation of Ge/C and Si/C rods. The ?1(?)
  fundamental was assigned at 1939.0 cm-1
• (D.L. Robbins et al, J. Chem. Phys. 2002 )
• In later work using single laser ablation of a
  sintered Ge/Si/C rod the yield of GeC3Si was
  improved. The ?4(?) stretching mode and the
  bending mode ?6(p) are tentatively assigned at
  824.7 cm-1 and 590.5 cm-1. 13C isotopic data are
  required to confirm the assignments

8
The ?4(?) stretching mode of linear GeC3Si
74-12-12-12-28, 824.7 cm-1
72-12-12-12-28, 825.3 cm-1
70-12-12-12-28, 826.0 cm-1
76-12-12-12-28, 824.2 cm-1
810
815
820
825
830
835
840
Frequency (cm-1)
9
1279.6
Linear GeC3 or SiC3 ?
1277.1
1257.0
1254.5
(a) 20 13C/Ge/Si sintered rod
1220
1230
1240
1250
1260
1270
1280
1290
Frequency (cm-1)
10
Linear GeC3
1279.6
(a) 35 13C/Ge sintered rod
1257.0
1257.0
1257.0
1257.0
1277.1
1277.1
1277.1
1254.5
1254.5
1254.5
1254.5
1232.7
1230.2
1232.7
1230.2
1232.7
1230.2
1232.7
1230.2
1232.7
1230.2
1232.7
1230.2
1252.7
1252.7
1252.7
1252.7
1252.7
1220
1230
1240
1250
1260
1270
1280
1290
Frequency (cm-1)
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GeC3 isomers (Leszczynski et al. J. Chem. Phys.
2005)
kite
0 kcal/mol
MP2 (CCSD) DFT
fan
2.1 kcal/mol
kJ/mol
linear
9.2 kcal/mol
kJ/mol
12
Theoretical calculations using B3LYP/cc-pVDZ
level of theory
kite
11.1 kcal/mol
13
Theoretical calculations using B3LYP/cc-pVDZ
level of theory
fan
7.4 kcal/mol
14
Theoretical calculations using B3LYP/cc-pVDZ
level of theory
linear
0 kcal/mol
15
A
(b) 35 13C/Ge sintered rod
1279.6
C
D, E
B
G
H
F
1254.5, 74-13-12-12 74-12-13-13
1277.1, 74-12-12-13
1257.0, 74-12-12-13
1232.7, 74 13-12-13
1230.2, 74-13-13-13
1252.7, 74-13-13-12
(a) DFT Simulation
1220
1230
1240
1250
1260
1270
1280
1290
Frequency (cm-1)
16
The ?2(s) mode of linear GeC3
aDFT calculations scaled by two scaling
parameters function (R. H. Kranze et al. ,JCP
1995)
17
Theoretical calculations using B3LYP/cc-pVDZ
level of theory
5.3 times the intensity of the 1279.6 cm-1 band
18
?C3
C6
?
9 peaks/10 cm-1

(a) 35 13C/Ge sintered rod

GeC3Ge
?
C9
?

C7
?
Frequency (cm-1)
19
?5

• Simultaneous ablation
• of 5 13C and Ge rods

? C6
1952.5
?3
GeC3Ge
GenCm ?
? unidentified weak features
1920.7
GeCO site
GeC9
? C6 natural enrichment single
substitutions
?1 ?
C6-
GeCO
GeC3
1928.3
1936.7
1918.9
?5
1907.7
C7
1903.9
?
?
?
?
?
?
?
?
Cn?
(b) Ablation of C rod
1880
1890
1900
1910
1920
1930
1940
1950
1960
1970
20
?3
GeCO site
(b) 5 13C and Ge dual ablation
GeC3Ge
GeCO
?3 GeC3Ge all 13C isotopic shifts
1907.7
1918.9
? ?5 C7 single 13C isotopic shifts
1920.7
?1
? ?4 C6 13C isotopic shift
GeC3
Ge13CO site
?5
C7
1903.9
Ge13CO

?
1876.4
?

1907.7
?
?
?

?
?

?

A
(a) DFT Simulation
B
C
D
1840
1850
1860
1870
1880
1890
1900
1910
1920
21
The ?1(s) mode of linear GeC3
aDFT calculations scaled by one scaling parameter

22
Laser ablation technique vs. GeC3 isomers

• We have experimental evidence that the laser
  ablation
• technique produces similar to Knudsen evaporation
• cell evaporation (Drowart et al., JCP 1959)
• 10 C2
• 30 C1
• 60 C3

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Laser ablation technique vs. GeC3 isomers

• We have experimental evidence that the laser
  ablation
• technique produces similar to Knudsen evaporation
• cell evaporation (Drowart et al., JCP 1959)
• 10 C2
• 30 C1
• 60 C3

convergence
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Laser ablation technique vs. GeC3 isomers

• We have experimental evidence that the laser
  ablation
• technique produces similar to Knudsen evaporation
• cell evaporation (Drowart et al., JCP 1959)
• 10 C2
• 30 C1
• 60 C3

25
Conclusions

• DFT calculations with B3LYP/cc-pVDZ level of
  theory predict the kite, fan, and linear isomers
  within a few kcal/mol. We think that the laser
  ablation technique favors the fan and linear
  isomers over the kite
• No experimental evidence of kite structure for
  MC3 (M Ge, Cr, Co, Al, Ti, Sc, Cu)
• (Kinzer et al., JCP. 2006,2008 Bates et al.,
  JCP, 2006,2007,2008 Vala et al. JCP 2008)
• Linear GeC3 was formed by the laser ablation
  technique. The ?1(s) and ?2(s) stretching modes
  have been observed at 1903.9 and 1279.6 cm-1
  respectively

26
Acknowledgments

• Our group would like to acknowledge funding from
• Welch Foundation
• TCU Research and Creative Activities Fund
  (TCURCAF)
• W.M. Keck Foundation
• Great appreciation for
• David Yale (machine shop)
• Mike Murdock (machine shop)
• Jerry Katchinska (electronics shop)