Volker Lutter, Laborastrophysik, Universität Kassel 69 th ISMS Champaign-Urbana, Illinois HIGH RESOLUTION INFRARED SPECTROSCOPY AND SEMI-EXPERIMENTAL STRUCTURES OF Si 2 C 3 AND Ge 2 C 3 Volker Lutter, Laborastrophysik, Universität Kassel, Germany +++

Volker Lutter, Laborastrophysik, Universität Kassel 69 th ISMS Champaign-Urbana, Illinois Theoretical Investigation C-chains and C-X-chains in quantum chemistry (ab initio methods) Extensively studied by Botschwina et al. Experimental Investigation C-chains and C-X-chains in the gas phase (Inert gas matrices and small XC, XC 2 excluded) C n : n=3,4,5,6,7,8,9,10,13 (IR, Saykally et al., Giesen et al.) SiC n : n=3,4,5,6,7,8 (mostly FTMW, SiC 4 also Infrared) SC n : n=4,5,6,7,8,9 (FTMW) SiC n S: n=2,3,4,6(FTMW) Symmetric carbon hetero clusters SC n S: n=3 SiC n Si: n=3 Motivation Experimental data from symmetric hetero clusters are underrepresented for linear carbon hetero clusters no permanent dipole moment

Volker Lutter, Laborastrophysik, Universität Kassel 69 th ISMS Champaign-Urbana, Illinois Structural (Fundamental) Chemistry and Symmetric Molecules Advantage Symmetric molecules exhibit less different bond lengths Less parameters enable 1.Higher possible computational levels (ab initio) 2.Lower computational costs at the same level of theory Symmetric chain like X 2 C 3 molecules provide benchmarks for quantum theory Disadvantage Symmetric molecules do not have a permanent dipole moment 1.Not accessible through microwave measurements 2.Experimental data need to be taken from infrared measurements How can we get access to symmetric carbon chain like hetero clusters? Which feedback can these data give to theoretical structure chemistry?

Volker Lutter, Laborastrophysik, Universität Kassel 69 th ISMS Champaign-Urbana, Illinois Experimental Setup IR Nd:YAG

Volker Lutter, Laborastrophysik, Universität Kassel 69 th ISMS Champaign-Urbana, Illinois In preparation, Lutter et. al. J. Krieg et al. Rev. Sci. Instrum. 82, (2011) S. Thorwirth, V.Lutter et al., J. Mol. Spectrosc. 270, (2011) Measurements Main Isotopologue of Si 2 C 3 3 = (14) cm -1 B 0 = (39) MHz   = 4.116(55) MHz   = -3.30(11) MHz ab initio 3 = cm -1 (CCSD(T)/cc-pV(T+d)Z)   = MHz (CCSD(T)/ cc-pV(Q+d)Z)   = MHz (CCSD(T)/ cc-pV(Q+d)Z)  B 0 = MHz (CCSD(T)/ cc-pV(Q+d)Z) All Carbon Substituted Si 2 13 C 3 3 = (2) cm -1 B 0 = (104) MHz   = 4.105(144) MHz ab initio 3 = cm -1 (CCSD(T)/ cc-pV(T+d)Z)   = MHz (CCSD(T)/ cc-pV(Q+d)Z)  B 0 = MHz (CCSD(T)/ cc-pV(Q+d)Z)

Volker Lutter, Laborastrophysik, Universität Kassel 69 th ISMS Champaign-Urbana, Illinois In preperation, Lutter et. al. J. Krieg et al. Rev. Sci. Instrum. 82, (2011) S. Thorwirth, V.Lutter et al., J. Mol. Spectrosc. 270, (2011) Measurements Main Isotopologue of Si 2 C 3 3 = (14) cm -1 B 0 = (39) MHz   = 4.116(55) MHz   = -3.30(11) MHz ab initio 3 = cm -1 (CCSD(T)/cc-pV(T+d)Z)   = MHz (CCSD(T)/ cc-pV(Q+d)Z)   = MHz (CCSD(T)/ cc-pV(Q+d)Z)  B 0 = MHz (CCSD(T)/ cc-pV(Q+d)Z) All Carbon Substituted Si 2 13 C 3 3 = (2) cm -1 B 0 = (104) MHz   = 4.105(144) MHz ab initio 3 = cm -1 (CCSD(T)/ cc-pV(T+d)Z)   = MHz (CCSD(T)/ cc-pV(Q+d)Z)  B 0 = MHz (CCSD(T)/ cc-pV(Q+d)Z) Semi-Experimental semi B e = MHz ae-CCSD(T)/cc-pwCVQZ calc B e = MHz deviation MHz semi B e = exp B 0  calc  B 0 ae-CCSD(T)/cc-pwCVQZ r C-C Å r Si-C = Å Semi-Experimental semi B e = MHz ae-CCSD(T)/cc-pwCVQZ calc B e = MHz deviation MHz semi B e = exp B 0  calc  B 0 ae-CCSD(T)/cc-pwCVQZ r C-C Å r Si-C = Å

Volker Lutter, Laborastrophysik, Universität Kassel 69 th ISMS Champaign-Urbana, Illinois What happens for larger atoms? 1.More electrons to be computed 2.Higher computational costs 3.Larger influence of electron correlations 4.Stronger relativistic effects Exchanging silicon atoms by germanium atoms 1.Ge 2 C 3 has same geometry as Si 2 C 3 2.Same electronic configuration 1  g 3.Comparable vibrational dipole moment (C-C asym. stretch.) 4.Matrix isolation measurement available (vibrational studies) E. Gonzalez, C. M. L. Rittby, W. R. M. Graham, J. Phys. Chem. 112, 43, , (2008) One Step Further

Volker Lutter, Laborastrophysik, Universität Kassel 69 th ISMS Champaign-Urbana, Illinois Main Isotopologue Experimental 74 GeC 3 74 Ge 3 = (9) cm -1 B 0 = (27) MHz   = 1.593(38) MHz ab initio (CCSD(T)/cc-pVTZ) 3 = cm -1   = MHz  B 0 = MHz semi B e = MHz CCSD(T)/cc-pwCVQZ calc B e = MHz semi B e = exp B 0  calc  B 0 Measurements

Volker Lutter, Laborastrophysik, Universität Kassel 69 th ISMS Champaign-Urbana, Illinois Measurements 74 GeC 3 74 Ge B 0 = (27)   =1.593(28) 74 GeC 3 72 Ge B 0 = (20)   =1.612(38) 74 GeC 3 70 Ge B 0 = (96)   =1.628(138) 72 GeC 3 72 Ge B 0 = (31)   =1.625(43) 72 GeC 3 70 Ge B 0 = (126)   =1.648(177) 70 GeC 3 70 Ge B 0 = (333)   =1.663(474) Experimental  B 0 = calc   =  B 0 = calc   =  B 0 = calc   =  B 0 = calc   =  B 0 = calc   =  B 0 = calc   = CCSD(T)/ cc-pVTZ All Values in MHz semi B e = calc B e  = semi B e = calc B e = semi B e = calc B e = semi B e = calc B e = semi B e = calc B e = semi B e = calc B e = Semi-Exp. vs CCSD(T)/cc-pwCVQZ

Volker Lutter, Laborastrophysik, Universität Kassel 69 th ISMS Champaign-Urbana, Illinois Can we derive a semi-experimental structure from these IR-data? Question

Volker Lutter, Laborastrophysik, Universität Kassel 69 th ISMS Champaign-Urbana, Illinois Semi-Experimental Structure Experimental data provide n different Isotopologues n=2 for SiC 3 Si and n=6 for GeC 3 Ge Zero-point vibrational corrections are available from CCSD(T) theory for both species. Semi-experimental rotational constants in the equilibrium are available semi B e = exp B 0  calc  B 0 Uncertainties are in the range of Å (for Si 2 C 3 ). Not helpfull! Fixed C-C bond length leads to precise values for the X-C distance Methode r C-C r Ge-C CCSD(T)/cc-pwCVQZ Å Å Semi-Exp. (Fixed at r C-C = Å) Å Methode r C-C r Si-C CCSD(T)/cc-pwCVQZ Å Å Semi-Exp. (Fixed at r C-C = Å ) Å

Volker Lutter, Laborastrophysik, Universität Kassel 69 th ISMS Champaign-Urbana, Illinois Conclusion C Å Å SiC 3 Si Å Å GeC 3 Ge Å Å Values in red from CCSD(T)/cc-pwCVQZ Values in black, semi-exp. values from this work

Volker Lutter, Laborastrophysik, Universität Kassel 69 th ISMS Champaign-Urbana, Illinois Dipl. Phys. Volker Lutter Laborastrophysik Universität Kassel Prof. Dr. Thomas Giesen Laborastrophysik Universität Kassel Dr. Sven Thorwirth Laboratory Astrophysics Universität zu Köln, Germany Prof. Dr. Jürgen Gauss Theoretische Chemie Universität Mainz, Germany Team / Funding Funding Deutsche Forschungsgemeinschaft TH 1301/3-1 and TH 1301/3-2

Volker Lutter, Laborastrophysik, Universität Kassel 69 th ISMS Champaign-Urbana, Illinois Thank you for your attention!

Volker Lutter, Laborastrophysik, Universität Kassel 69 th ISMS Champaign-Urbana, Illinois Semi-Experimental Structure Methode r C-C r Ge-C CCSD(T)/cc-pwCVQZ Å Å Fixed r C-C = Å ANO-RCC-unc Å Å ANO-RCC-unc/SFX2c-1e Å Å rel. contraction Å Å