Vibrational energies for acrylonitrile from 66th OSU International Symposium on Molecular Spectroscopy MH09 Vibrational energies for acrylonitrile from mm-wave to THz rotational spectra Zbigniew Kisiel,a Lech Pszczółkowski,a Brian J.Drouin,b Carolyn S.Brauer,b Shanshan Yu,b John C.Pearson,b Ivan R.Medvedev,c Sarah Fortman,d Christopher Neesed aInstitute of Physics, Polish Academy of Sciences, Warszawa, Poland bJet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109-8099 cDepartment of Physics, Wright State University, Dayton, OH 45435 dDepartment of Physics, The Ohio State University, Columbus, OH 43210

Fermi + c-axis Coriolis: DE = 228.29991(2) cm-1 The lowest vibrational states in acrylonitrile: Kisiel, Pszczolkowski, Drouin, Brauer, Yu, Pearson, J.Mol.Spectrosc. 258, 26 (2009) Fermi + c-axis Coriolis: DE = 228.29991(2) cm-1 Only DE + one Coriolis (Fab) + three Fermi (WK, WJK, WKK ) interaction constants were necessary

Principal perturbations identified in aR-type g.s. transitions: Differences relative to effective single state fits are plotted. g.s. lines 11 = 1 lines Broadband coverage possible well into the THz region with single scans reaching frequency spans of 100 GHz. Ka = 6 Ka = 4

Ka = 10 Isotopic confirmation of the gs  n11 coupling model: calc = CCSD(T)  6-31G(d,p) H2C=CDCN Ka = 10 Krasnicki, Kisiel, Drouin, Pearson, J.Mol.Struct. (2011), in press.

First set of spectra measured with the cascaded frequency multiplication spectrometer at jpl: Drouin, Mailwald, Pearson, Rev.Sci.Instr. 76, 093113 (2005) Broadband coverage possible well into the THz region with single scans reaching frequency spans of 100 GHz.

TOTAL COVERAGE = 1098 GHz The recorded spectra: Praha2008 The recorded spectra: Spectra were recorded at JPL and OSU using cascaded harmonic generation techniques and were merged into a single file TOTAL COVERAGE = 1098 GHz spectra/GHz span/GHz 210 - 270 60 290 - 320 30 390 - 560 170 560 - 640 80 818 - 847 29 850 - 930 80 950 - 1205 255 1576 - 1626 50 1648 - 1668 20 1685 - 1900 215

perturbation behaviour Analysis tools: AABS package + SPFIT/SPCAT: Praha2008 Loomis-Wood display option T for plotting perturbation behaviour

The strong n11  n15 Coriolis coupling dilemma: A /MHz effective 2Aza gs 49850 49850 v11 =1 49170 49926 v15 =1 50802 49873 za11,15 = 0.625 But there is also coupling about the b-axis: zb11,15 = 0.165 while similar 2Bzb behaviour is NOT observed v15 =1 gs v11 =1 =2 =3 Cazzoli+Kisiel, J.Mol.Spectrosc 130, 303 (1988)

Selective perturbations for n11  n15 coupling : as manifested in aR-type transition at high-J values Ka = 4 Ka = 9 Ka = 5 v15 = 1 Ka = 11 Ka = 14 Ka = 3 J’’max = 55 533 GHz v11 = 1 J’’max = 93  885 GHz

bQ-branch for v11=1, Ka = 14  13 : J = 54+55 J = 56+57 Obs. Calc.

Matching bQ-branch for v15=1, Ka= 12  11 : …but lines in this band are not yet well fitted since the Ka= 12 levels of v15=1 couple with the Ka= 8 levels of v11=2 J = 54+55 J = 57 J = 56 Obs. Calc.

Key results from fit of gs  n11  n15 coupling : A /MHz 49850.69586(60) 49170.4528(15) 50802.0623(32) B /MHz 4971.212543(50) 4990.77289(11) 4974.34091(19) C /MHz 4513.828366(52) 4521.96698(10) 4522.99857(17) DJ /kHz 2.244078(16) 2.269235(33) 2.240545(70) DJK /kHz -85.5693(27) -76.6554(25) -92.9977(29) DK /kHz 2715.365(12) 2171.302(29) 3280.906(84) dJ /kHz 0.4566465(38) 0.467868(13) 0.452400(31) dK /kHz 24.5241(18) 27.1878(38) 25.413(17) DE /MHz 6844255.82(46) 9973437.81(50) A total of 7045 lines fitted at srms=1.37 Same interaction constants (4 Fermi+1 Coriolis) for the gs  n11 interaction as in the JMS2009 paper A total of four a- and b-axis Coriolis constants for the n11  n15 interaction

(v11 = 1, v15 = 1) v10 = 1 Dyad near 570 cm-1: n10  n11 n15 coupling The interaction is a- and b-axis Coriolis resonance and in aR-type transitions is maximized at moderate values of J (and visible for very low Ka) Ka = 3 Ka+Kc=J+1 Ka = 3 Ka+Kc=J (v11 = 1, v15 = 1) Ka = 2 Ka+Kc=J+1 Ka = 2 Ka+Kc=J J’’max = 46  450 GHz J’’max = 30  295 GHz v10 = 1

Key results from fit of n10  n11 n15 coupling : lower state upper state A /MHz 49517.341(52) 49924.15(12) fitted lines = 1650 B /MHz 4965.8468(77) 4992.5381(77) rms = 1.4 C /MHz 4509.60997(62) 4531.58428(68) DJ /kHz 2.20301(20) 2.27173(19) DJK /kHz -89.0219(84) -81.487(10) DK /kHz 2712.87(18) 2551.9(55) dJ /kHz 0.44432(12) 0.46804(12) dK /kHz 22.0828(84) 25.579(14) DE /MHz 71687.20(51) + 7 other Ga,Gb based interaction constants LOWER = n10 UPPER = n11,n15 expt calc* expt calc* Av-A0 /MHz -333.36 -326.14 73.45 226.57 Bv-B0 /MHz -5.366 -5.79 21.326 24.22 Cv-C0 /MHz -4.218 -4.20 17.756 17.46 *CCSD(T)/6-31G(d,p)

Vibrational energies from perturbations: Two state fit: E(v11 =1, v15 =1) - E(v10 =1) = 2.39123(2) cm-1 Three state fit: this work FIR* v11 =1 228.29980(2) 228.83(18) v15 =1 332.67808(2) 332.91(9) * Cole+Green, J.Mol.Spectrosc. 48, 246 (1973)

Praha2008 SUMMARY: The coverage of the room temperature rotational spectrum of acrylonitrile has been increased in extent to a total of 1098 GHz and in the upper frequency limit to 1.9 THz Several specific n11  n15 perturbations have been identified and fitted in the interaction scheme gs  n11  n15 The precise values of E11= 228.29980(2) cm-1 and E15 = 332.67808(2) cm-1 are consistent with those from gas-phase FIR determination For the two closely spaced states near 570 cm-1 a successful n10  n11 n15 coupled fit was achieved, and the states were assigned unambiguously on the basis of Bv-B0 values calculated from the ab initio anharmonic force field Identification of further specific interactions (in particular those affecting 2n11 ) is in progress in order to incorporate the g.s. and the five lowest vibrational states into a single coupled fit