Torsional Splitting in the Rotational Spectrum from 8 to 650 GHz of the Ground State of 1,1-Difluoroacetone L. Marguls, R. A. Motiyenko, Universit de Lille P. Groner, UMKC F. De Chirico, A. Turk, S. A. Cooke, Purchase College Motivation Structural studies on various halogenated acetones using microwave spectroscopy in the 8 18 GHz region The spectral analysis of 1,1-difluoroacetone had an interesting feature: Spectroscopic constants for 1,1-difluoroacetone (ERHAM) Talk RH04 Columbus 2011 G. S. Grubbs II, P. Groner, Stewart E. Novick and S. A. Cooke. J. Mol. Spectrosc. 280, (2012). ParameterS-reductionParameterA-reductionParameterNon- reduced IrIr III r IrIr IrIr D J / kHz2.705(34)-0.797(51) J / kHz 0.01(28)0.913(59)D J / kHz2.686(34) D JK / kHz (73) (47) JK / kHz 0.76(58)10.299(79)D JK / kHz-1.755(62) D K / kHz0.521(54) (12) K / kHz -13.8(43) (52)D K / kHz0.410(74) d 1 / kHz (33)-0.210(14) J / kHz (27)0.211(13)d J / kHz (54) d 2 / kHz (95) (70) k / kHz (18)-3.640(27)d K / kHz1.1246(52) R 5 / kHz1.46(67) / MHz Centrifugal distortion constants, fit to only the A torsional substate rotational transitions of 1,1-difluoroacetone Table 8.14 in Gordy & Cook Kivelson, Wilson, JCP, 21 (1953) 1229 Motiyenko et al, JMS, 264 (2010) 94 New measurements performed at Lille: Frequency range 150 GHz 600 GHz. Sample cell is a stainless steel tube, 6cm in diameter, 220 cm in length. Sample pressure is approximately 30 microbar Spectra recorded at room temperature Bp = 45.5 o C Vapor pressure = 0.47 bar at 25 o C b = 1.3 D, a = c = 0 = -0.93 Examples of spectra: 160 GHz 170 GHz Examples of spectra: GHz GHz Examples of spectra: Assignment strategy AABS package: Assignment strategy The AABS package is easy to use with SPFIT/SPCAT It readily adds quantum number assignments and exptl frequencies to a.lin file. Utility program LINERH from PROSPE converts.lin file format to ERHAM file format. Spectral constants obtained using ERHAM see talk WH01, Latest revision of the ERHAM code. Analysis is ongoing Currently working with 2483 transitions 1600 distinct frequencies Tentative: J < 74, K a < 65 Potentially problems with assignments of J > 50, K a > 30. For many E-substate transitions, alternate J assignments might be possible than those currently in the fits. Current best fit ParametermmW + MWMW (49) (99) / deg 63.58(11)65.312(16) A / MHz (34) (21) B / MHz (11) (13) C / MHz (11) (13) D J / kHz (33)2.682(29) D JK / kHz (58) (62) D K / kHz (67)0.550(50) d 1 / kHz (21) (23) d 2 / kHz (58) (13) Current best fit - continued ParametermmW + MWMW H J / Hz (67) H JK / Hz (22) H KJ / Hz (67) H K / Hz (55) h 1 / Hz (47) h 2 / Hz (2) h 3 / Hz (53) L K / mHz (67) L KJ / mHz (11) L KKJ / mHz (96) L JK / mHz (3) L J / mHz (41) l 1 / mHz (29) l 2 / mHz (17) l 3 / mHz (97) l 4 / mHz (28) N/A This is good news! Current best fit - continued ParametermmW + MWMW / MHz (13) (35) / MHz -1.43(20)2.91(23) / MHz 0.327(94) / MHz 0.036(14) [P z ] 1 / MHz 0.474(44) [P x ] 1 / MHz -0.37(12) [A-(B+C)/2] 1 / kHz 10.3(11)5.04(63) [D K ] 1 / Hz 4.60(34) [(B+C)/2] 1 / kHz -2.66(50) -4.4(11) [D JK ] 1 / Hz -3.97(33) [D J ] 1 / Hz 0.86(12) [D ab ] 1 / MHz (14) [(B-C)/4] 1 / kHz -1.61(25) -1.94(45) [d 1 ] 1 / Hz 1.010(81) [d 2 ] 1 / Hz 0.506(21) Best fit summary 41 parameters used 2483 transitions, 1600 distinct frequencies Approximately 60 transitions discarded Quartic, sextic and octic CD constants required for fit Current weighted standard deviation is 1.142, which corresponds to 6.85 kHz for MW transitions, and 57.1 kHz for the mm/sub-mm transitions Future work: Review of problem transitions Many more lines to add in to the fit Ultimately, further examine the Hamiltonian dependence Thank you