Acetaldehyde: Into the Submillimeter Brian J. Drouin, Herbert M. Pickett California Institute of Technology, Jet Propulsion Laboratory Pasadena, CA 91109-8099

Outline Motivation Previous Work New Data Current Fit Future Plans

Motivation Astronomy Spectroscopy Chemistry Highly abundant in ISM Bright and messy (weed or flower?) Spectroscopy Strong theoretical background Test case for low-barrier fitting routines Improve IAMCALC/SPFIT Chemistry Look for geminol?

Previous Work A. Bauder, F. J. Lovas, and D. R. Johnson, 1976, J. Phys. Chem. Ref. Data, 5, 53. (vT = 0) I. Kleiner, M. Godefroid, M. Herman, and A. R. W. McKellar, J. Mol. Spectrosc. 142, 238, 253 (1990) (vT = 1  0) I. Kleiner, J. T. Hougen, R. D. Suenram, F. J. Lovas, and M. Godefroid, J. Mol. Spectrosc. 148, 38-49 (1991). (vT = 0, FT fix) I. Kleiner, J. T. Hougen, R. D. Suenram, F. J. Lovas, and M. Godefroid, J. Mol. Spectrosc. 153, 578-586 (1992). (vT = 0,1 global) W. L. Barclay, Jr., M. A. Anderson, L. M. Ziurys, I. Kleiner, and J. T. Hougen, Astrophys. J. Suppl. 89, 221-226 (1993). (vT = 0,1;< 325 GHz)  S. P. Belov, M. Yu. Tretyakov, I. Kleiner, and J. T. Hougen, J. Mol. Spectrosc. 160, 61-72 (1993). (vT = 2)

The back-story Original MW was ugly FIR spectrum FTMW Typical for an asymmetric internal rotor though Barrier and structure good FIR spectrum Minimal assignments due to congestion Assignments inconsistent with MW FTMW New assignments – global fit possible

SPFIT Then and Now Then JPL catalog entry 1980 A. Bauder, F. J. Lovas, and D. R. Johnson, 1976, J. Phys. Chem. Ref. Data, 5, 53. A state - Asymmetric top rigid rotor E State - Pa, PaP2, PaP4, Pa3, Pa3P2, and Pa5 terms. The fit produced observed--calculated frequencies that were 3.5 times the experimental uncertainties in an RMS sense. Now Internal Axis Method ‘front end’ IAMCALC Set up A and E states for 3,6,9… “vibrational states” to form torsional basis Generate Fourier terms from Mathieu function – big ‘par’ file Run SPFIT/SPCAT as usual Iterate through IAMCALC as necessary Start with Kleiner’s vT = 0,1,2 assignments – verify and improve with new data

Theory Phenomenological periodic solutions to Mathieu Equation for one ‘vibration’ ‘Global’ analyses using torsional basis set

The “IAM” file Define r, n, Max M, Max v = 3*max vT Max series Flags: 0.3286316 3 66 -21 -26 99 3 0 12225059 / V3 99 6 0 -375172 / V6 99 0 2 228707 / F 99 3 2 1911 /-2*k7 -99 0 2 -1911 /-2*k7 200099 0 1 1.281 /-2*F*rho 200199 0 1 -0.22349 / Lv 201099 0 1 3.8284 / k1 220099 0 1 -0.06176 / c4 401099 0 1 -1.5757 / del_ab 200299 0 1 -3.487E-06 / lv 201199 0 1 0.05585E-03 / lamv 202099 0 1 -0.4385E-03 / lk 220199 0 1 0.138E-06 / c4J 221099 0 1 0.03389E-03 / c10 200099 0 3 8.0973 / k3 200199 0 3 -2.5E-06 / k3J 201099 0 3 -3.117E-03 / k3K 220099 0 3 -0.1960E-03 / c12 401099 0 3 0.571E-03 /del_ab3 200099 0 5 -0.01312 / ?? 1099 0 0 46735.4155 / A-(B+C)/2 199 0 0 9771.0219 / (B+C)/2 40099 0 0 341.25074 / (B-C)/4 610099 0 0 -3678.766 / Dab 199 3 0 -17.1563 / -Fv -199 0 0 17.1563 / -Fv 1099 3 0 578.294 /-k5 -1099 0 0 -578.294 /-k5 40099 3 0 -3.10243 /-c2/2 -40099 0 0 3.10243 /-c2/2 610099 3 0 -62.8780 /-dab -610099 0 0 62.8780 /-dab 1099 6 0 8.945 /-K2 -1099 0 0 -8.945 /-K2 299 0 0 -9.52171E-03 /-DJ 1199 0 0 0.03659 /-DJK 2099 0 0 -0.69782 /-DK 299 3 0 0.22250E-03 /-fv -299 0 0 -0.22250E-03 /-fv 1199 3 0 -0.254E-03 /-k5J -1199 0 0 0.254E-03 /-k5J 2099 3 0 -0.03797 /-fk -2099 0 0 0.03797 /-fk 40199 0 0 -2.19782E-03 /-dJ 41099 0 0 -0.02213 /-dK 610199 0 0 0.024294 / DabJ 611099 0 0 0.11337 / DabK 610299 0 0 0.2069E-06 / DabJJ 611199 0 0 7.55E-06 / DabJK 612099 0 0 0.04130E-03 / DabKK 399 0 0 1.224E-09 / HJ 1299 0 0 -1.324E-06 / HJK 2199 0 0 -0.02124E-03 / HKJ 3099 0 0 0.06889E-03 / HK 41199 0 0 -0.732E-06 / hJK 42099 0 0 -2.48E-06 / hK 99 0 6 0.02374 /k6? 99 0 4 -13.8868 / k4 199 0 4 0.0377E-03 / Mv 40099 0 4 -0.0549E-03 / c3 199 0 2 -0.08941 / Gv 1099 0 2 -12.9636 / k2 40099 0 2 -0.04620 / c1 610099 0 2 1.2011 / Del_ab 299 0 2 -1.304E-06 / gv 1199 0 2 -0.0114E-03 / k2J 2099 0 2 1.657E-03 / k2K 40199 0 2 -1.380E-06 / c1J 41099 0 2 0.1451E-03 /c3c 410099 -3 0 57.64 / Dac 40199 3 0 0.04473E-03 / c6 -40199 0 0 -0.04473E-03 / c6 41099 3 0 -0.578E-03 / c9 -41099 0 0 0.578E-03 / c9 200199 3 1 0.0991 / k6J 199 3 2 0.2543 / k7J or Ov 201099 3 1 -0.335 / K4 40099 6 0 -0.03055 / c11 610099 6 0 1.484 /ddab 220099 3 1 3.11E-03 / c22 1099 0 4 -5.036E-03 / ?? 401099 3 1 0.1923 / ddel_ab / 1 0 0 2.42340E+00 /mu_a / 2 0 0 -1.26580E+00 /mu_b Define r, n, Max M, Max v = 3*max vT Max series Flags: Choose type of series ++Fourier - integer K Parameters: Commutators and ½ anticommutators

New Data 499 GHz 500 GHz 490 GHz 500 GHz 430 GHz 500 GHz

New Data 570 GHz 625 GHz

New Data 770 GHz 850 GHz

New Data 850 GHz 930 GHz

New Data g.s. rQ11 (simulation shifted 0.5 MHz from prediction based on current fit) 1075.5 GHz 1076 GHz

New Data g.s. rQ12 E A 1167 GHz 1170 GHz

Current Fit >3800 transitions (1200 previous from < 339 GHz) Removed FIR (for now) and low res MW Current fit is reduced rms 1.2 0.00035 cm-1 FIR, 120 kHz MW < 608 GHz assigned J < 51, K < 21 1517 loops

Current Fit One iteration is 130 Seconds for 1.6 GHz system . rQ12 Assignments straightforward, fringe assignments are 300 kHz residuals Slowly improve parameters and close loops

Future Plans Assign vT < 3 data through 1200 GHz Achieve high quality analysis Publish and update catalog

Acknowledgements NASA - Astrophysics R&A Herschel Lab Support Kleiner code as verification for Hamiltonian

Multiplier Data & Collaborations * manuscript submitted/accepted