Millimeter- Wave Spectroscopy of Hydrazoic acid (HN 3 ) Brent K. Amberger, Brian J. Esselman, R. Claude Woods, Robert J. McMahon University of Wisconsin June 18, 2014

Previous Work on HN 3 Kewley, R.; Sastry, K. V. L. N.; Winnewisser, M., Journal of Molecular Spectroscopy 1964, 12, Bendtsen, J.; Winnewisser, M., Chemical Physics Letters 1975, 33, Bendtsen, J.; Winnewisser, M., Chemical Physics 1979, 40, Herzberg, G.; Patat, F.; Verleger, H., Z. Elektrochem. Angew. Phys. Chem. 1935, 41, ’s 1960’s- 1970’s 1980’s- 1990’s Bendtsen, J.; Hegelund, F.; Nicolaisen, F. M., Journal of Molecular Spectroscopy 1986, 118, 12. Hegelund, F.; Bendtsen, J., Journal of Molecular Spectroscopy 1987, 124, Bendtsen, J.; Hegelund, F.; Nicolaisen, F. M., Journal of Molecular Spectroscopy 1988, 128, Bendtsen, J.; Nicolaisen, F. M., Journal of Molecular Spectroscopy 1991, 145, Bendtsen, J.; Nicolaisen, F. M., Journal of Molecular Spectroscopy 1992, 152, Bendtsen, J.; Guelachvili, G., Journal of Molecular Spectroscopy 1994, 165, Hansen, C. S.; Bendtsen, J.; Nicolaisen, F. M., Journal of Molecular Spectroscopy 1996, 175,

The Synthesis Dry Ice Trap To Spectrometer H 2 O or D 2 O NaN 3 or Na 15 NNN Access to: HNNN DNNN H 15 NNN / HNN 15 N D 15 NNN / DNN 15 N

Our Spectrometer ~ GHz range 20 mTorr sample Room temperature

CCSD(T)/ANO2 Structure Å ° ° Å Å a b

Predicted Spectra for HN 3 and DN 3 HN 3 DN 3 Our Range

K=2 K=0 K=3 K=4 K=5 K=6 K=7 K=1 R- Series Anatomy HN 3 J = 13  12

The Spectrum: Full Range GHz J = 14  13 J = 15  14 J = 13  12 J = 11  10 J = 12  11 J = 10  9

The Spectrum: Key Features HN 3 J = 13  12 H 15 NNN J = 13  12 HNN 15 N J = 13  12 K=1 K=0 Vibrationally excited modes  

The Spectrum: H 15 NNN K=0 K=2 K=3 K=4 K=5 H 15 NNN at natural isotopic abundance J = 13  12

Finding Naturally Occurring Center 15 N Loomis- Wood plots centered on H 14 N 3 lines were used to find corresponding HN 15 NN lines

The fit data: HN 3 Bendtsen and Winnewisser 1975 (MHz) Present Work (MHz) CCSD(T)/ANO2 (MHz) A (6.0) (46) B (50) (47)11989 C (50) (48)11737 DJDJ (35) (33) D JK (11) (21)0.904 DKDK [230][0]224 djdj (27) (54) dkdk [0]0.388(23)0.379 HJHJ (36) (13) H JK (86) (17) H KJ (35) (20) HKHK [0] L KKJ (55) Bendtsen, J.; Winnewisser, M., Chemical Physics Letters 1975, 33,

Summary of Isotopologues HNNNH 15 NNNHN 15 NNHNN 15 NH 15 N 15 NNH 15 NN 15 NHN 15 N 15 N A (MHz) (46) (68) (52) (89) (730) (332)? B (MHz) (47) (11) (21) (49) (83) (42)? C (MHz) (48) (11) (21) (49) (81) (41)? n ? DNNND 15 NNNDN 15 NNDNN 15 ND 15 N 15 NND 15 NN 15 NDN 15 N 15 N A (MHz) (24) (21) (51) (25) (18) (18) (32) B (MHz) (26) (31) (67) (31) (11) (13) (19) C (MHz) (27) (25) (67) (27) (12) (13) (18) n Cannot access H 15 N 15 N 15 N or D 15 N 15 N 15 N

R e Structure Determination Experimental constants were corrected for vibration- rotation interaction and electron mass. Using xrefit module in CFOUR: Fit 5 structural parameters to 39 moments of inertia (63) Å (14) Å (15) Å (64)° (19)° b a

Structure Comparison CCSD(T)/ANO2 (R e ) xrefit (R e )Substitution Structure (R s ) R 1 (Å) (15)1.159(50) R 2 (Å) (14)1.204(61) R 3 (Å) (63)1.017(12) A1A ° °(64)108.0°(21) A2A °171.14°(19)171.26°(57) R3R3 R2R2 R1R1 A1A1 A2A2

Excited Vibrational States HN 3 DN 3 Ground ν5ν5 ν6ν6 ν4ν4 2ν52ν5 2ν62ν6 ν 5 + ν 6 ν3ν3 0 cm cm cm cm cm -1 ~ cm -1 ~1213 cm -1 ~1074 cm cm -1 0 cm cm cm -1 ~991 cm -1 ~1082 cm cm cm -1 Ground ν5ν5 ν6ν6 ν4ν4 2ν52ν5 2ν62ν6 ν 5 + ν 6 ν3ν3 Coriolis perturbation Centrifugal distortion perturbation

Past IR Work -A large body of work analyzing each rotationally-resolved band in HN 3 and DN 3 IR spectra has been published. -Rotational constants and coupling terms from IR data has been published. -Published data does not adequately predict lines for vibrationally excited states in our millimeter-wave spectra. -The published data is still an outstanding starting point for our own analysis. Hegelund, F.; Bendtsen, J., Journal of Molecular Spectroscopy 1987, 124, Bendtsen, J.; Hegelund, F.; Nicolaisen, F. M., Journal of Molecular Spectroscopy 1988, 128, For our analysis of ν 5 and ν 6 the literature gives us starting points for the rotational constants and 3 separate Coriolis terms: Z a, η bc and Z b. Also provides very accurate energy separation between states. The published high-resolution rovibrational transitions allow us to calculate where the pure rotational transitions should be.

Finding HN 3 ν – ν 5 Ground Calculated from R- branch IR transitionsCalculated from P- branch IR transitions MHz MHz Error of cm -1 = 30 MHz

Initial Assignments of ν 5 and ν 6 Lines Calculated from P-branch IR transitions Calculated from R-branch IR transitions

Initial Assignments of ν 5 and ν 6 Lines Lines assigned based on rovibrational transitions

Fit for States ν 5 and ν 6 of HN 3 Actual Fit!

Combined fit for ν 5 and ν 6 of HN 3 ν5ν5 Present WorkHegelund et al A (2800)590240(19) B (30) (66) C (30) (66) ν6ν6 Present WorkHegelund et al A739181(3458)623487(19) B (271) (66) C (271) (66) Present WorkHegelund et al ZaZa (32)*10 6 [1.141*10 6 ] η bc 9.30 (19)9.65(24) ZbZb (30)1874.3(39) E[ ]

Combined fit for ν 5 and ν 6 of DN 3 ν5ν5 Present WorkHegelund et al 1987 A (17)327613(12) B (11) (57) C (97) (57) ν6ν6 CurrentHegelund et al 1987 A (14)361742(36) B (84) (57) C (66) (57) Present WorkHegelund et al 1987 ZaZa (42)[565409] η bc (12)4.80(90) ZbZb (79)2130(180) E[ ]

Summary and Ongoing Work Best structure of HN 3 to date (63) Å (14) Å (15) Å (64)° (19)° Find more lines, especially B-type lines to tighten up the fits. Accomplished: In Progress: Combined fits for Coriolis coupled ν 5 and ν 6 states. Investigate the complex coupling patterns of the higher energy vibrationally excited states.

Thanks for Listening! McMahon group + R.C. Woods