and analysis of hyperfine structure from four quadrupolar nuclei 71st International Symposium on Molecular Spectroscopy WE06 Rotational spectroscopy of CF2ClCCl3 and analysis of hyperfine structure from four quadrupolar nuclei Zbigniew Kisiel, Ewa Białkowska-Jaworska, Lech Pszczółkowski, Institute of Physics, Polish Academy of Sciences, Warszawa, Poland Iciar Uriarte, Francisco J. Basterretxea, Emilio J. Cocinero Departamento de Quimica Fisica, Universidad del Pais Vasco, (UPV-EHU), Bilbao, Spain

Johannes C. Laube et al., Praha2008 Analysis of 1978-2012 air samples from Tasmania + Analysis of air bubbles in Greenland snow Four previously undetected ozone-depleting substances identified: CFC-112 = CFCl2CFCl2 CFC-112a = CF2ClCCl3 CFC-113a = CF3CCl3 HCFC-133a = CF3CH2Cl CFC-112a = CF2ClCCl3 has not yet been studied by rotational spectroscopy (small  , b-type spectrum and 4Cl)

The chirped-pulse rotational spectrum of CF2ClCCl3: Praha2008 CFC-112a  parent 551  440 550  441 transition region Cl2 Cl1 Cl3 Initial A,B,C determined

Hyperfine structure (4 chlorine nuclei): Praha2008 CFC-112a 441  330 440  331 Obs. 3 asymmetric rotor quantum numbers + 4 spin quantum numbers = 7: Fortunately symmetric top quantisation allows using 2 + 4 = 6 quanta First prediction

Praha2008 Predictions: Accurate predictions of hyperfine structure are the key to success. There are several possibilities: Use the W.C.Bailey approach: ab initio calculation at equilibrium geometry with extended basis set tailored to the specific quadrupolar nucleus, see: http://nqcc.wcbailey.net/ Use general scaling coefficients: see Białkowska-Jaworska et al., J.Mol. Spectrosc. 238, 72 (2006) Use specific scaling based on related molecules: H-CCl3, H3C-CCl3, NC-CCl3 SPFIT/SPCAT package is the tool of choice, but the standard (32-bit) compilation runs into „Memory allocation error” for this molecule (Hamiltonian sizes > 7800). 64-bit executables for Windows and Linux are now available on the PROSPE website: http://info.ifpan.edu.pl/~kisiel/asym/asym.htm#64bit

Chirped pulse identification allowed making F-P scans: Praha2008 Chirped pulse identification allowed making F-P scans: 431  322 Chirped pulse FWHH  90 kHz FWHH  18 kHz Cavity

F-P scans allowed assignment: Praha2008 Pattern matching becomes possible 441  330 440  331 Obs. transition in the fit Calc.

And in more detail: 441  330 440  331 Obs. Calc. Praha2008 And in more detail: 441  330 440  331 Obs. Complex blends are avoided and only clear transitions picked out for analysis Calc.

Also for the 431  322 transition: Praha2008 Also for the 431  322 transition: Obs. Calc.

And in more detail: Obs. 431  322 Calc. Settable frequency marker Praha2008 And in more detail: Obs. 431  322 Settable frequency marker (V and ^V in ASCP_L) Calc.

Rotational and centrifugal constants: Praha2008 Rotational and centrifugal constants: --------------------------------------------------------------------- chirped/ASFIT cavity/SPFIT MP2/aug-cc-pVTZ A /MHz 1236.833(32) 1236.843683(84) 1235.9 B /MHz 921.278(63) 921.25227(10) 925.3 C /MHz 878.234(31) 878.23725(10) 882.2 DJ /kHz [ 0.0363 ] 0.0344(27) DJK /kHz [ 0.0187 ] [ 0.0187 ] DK /kHz [-0.00804] [-0.00803] dJ /kHz [ 0.00252] [ 0.00252] dK /kHz [ 0.0340 ] [ 0.0340 ] Nlines 19 301 Ntrans 19 15 sigma /kHz 862. 2.316 rms 0.8621 1.158 The number of different measured frequencies The number of different rotational transitions

Nuclear quadrupole coupling constants: Praha2008 ------------------------------------------------------------- predicted experimental scaled Bailey SPFIT Cl1 = in-plane Cl in the CCl3 group: 1.5Xaa /MHz -39.02 -38.75 -37.4695(66) (Xbb-Xcc)/4 /MHz -14.59 -14.71 -14.8246(22) Xab /MHz -61.11 61.63 -61.50(12) Cl2 = out-of-plane Cl in the CCl3 group: 1.5Xaa /MHz 59.87 60.74 59.9635(37) (Xbb-Xcc)/4 /MHz 10.91 11.08 10.93725(84) Xab /MHz 5.94 5.55 6.307(80) Xac /MHz 7.12 6.83 7.70(19) Xbc /MHz -57.33 -57.72 -57.4297(43) Cl3 = in-plane Cl in the CF2Cl group: 1.5Xaa /MHz -53.01 -53.51 -52.5314(64) (Xbb-Xcc)/4 /MHz -10.63 -10.77 -10.8393(24) Xab /MHz -54.56 55.54 -55.37(12) Average prediction accuracy: scaled 2.2 % Bailey 3.1 %

 Principal nuclear quadrupole tensors: aa ab ac za zz 0 0 Praha2008 Principal nuclear quadrupole tensors: aa ab ac ab bb bc ac bc cc zz 0 0 0 xx 0 0 0 yy   = (xx - yy)/zz za QDIAG zz = - 82.69(12) MHz  = 0.0192(15) zz = - 82.25(3) MHz  = 0.0216(21) zz = - 77.07(12) MHz  = 0.0169(15) H-CCl3 zz = - 78.688(18) MHz F-CC-Cl zz = - 83.0(1) MHz H3C-CCl3 zz = - 78.218(14) MHz

Praha2008 CONCLUSIONS: Assigning completely resolved quadruple quadrupolar problems is possible but accurate prediction is the key to success Suitable combination of supersonic expansion techniques was important for CFC-112a : initial assignment with chirped pulse and follow up measurements with the cavity The hyperfine information for CF2ClCCl3 allows interesting comparisons with other molecules such as related triple-chlorine molecules CHCl3, CH3CCl3 and with chloro-fluoro species The hyperfine angles za provide useful additional information for structure determination The CFC-112a molecule has been „tamed”: basic high resolution spectroscopic constants have been determined