The rotational spectrum of 2-iodobutane (sec-butyl-iodide) has been collected from 5.5-16.5 GHz using jet-pulsed Fourier transform microwave spectroscopy on both broadbandBrown, G. G.; Dian, B. C.; Douglass, K. O.; Geyer, S. M.; Shipman, S. T.; Pate, B. H. Review of Scientific Instruments 2008, 79, 053103.nd Balle-Flygare cavityBalle, T.; Flygare, W. Review of Scientific Instruments 1981, 52, 33-45.nstruments. Transitions belonging to three unique conformers were observed, namley the gauche-, anti-, and gauche′- species. All four ¹³C isotopologues of the gauche-2-iodobutane were observed. The complete nuclear quadrupole coupling tensor of iodine has been determined for all conformers and ¹³C isotopologues. A comparison between these nuclear quadrupole coupling tensors and those of similar iodine-containing molecules will be presented. Changes in the quadrupole coupling of iodine upon isotopic substitution will also be discussed. Additionally, isotopic substitution in conjunction with ab initio calculations allowed for both an r_s and r₀ structural analysis of gauche-2-iodobutane.

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Brown, G. G.; Dian, B. C.; Douglass, K. O.; Geyer, S. M.; Shipman, S. T.; Pate, B. H. Review of Scientific Instruments 2008, 79, 053103.a Balle, T.; Flygare, W. Review of Scientific Instruments 1981, 52, 33-45.i

The rotational spectrum of 1-iodobutane was measured in a frequency range of 7-13 GHz, revealing a dense set of rotational transitions. Over 400 of the observed transitions were assigned to three different low energy conformational isomers. A previous low resolution microwave studySteinmetz, W. E.; Hickernell, F.; Mun, I. K.; Scharpen, L. H. J. Mol. Spectrosc. 1977, 68, 173-182.f 1-haloalkanes, including 1-iodobutane, confirmed that the three conformers present are the anti-anti, gauche-anti, and gauche-gauche species. From this high resolution study, the complete nuclear quadrupole coupling tensor of iodine was determined for each conformer. Rotational, centrifugal distortion, nuclear spin-rotation coupling constants will be discussed. Nuclear quadrupole coupling constants will also be presented and compared to other iodoalkane species. r0pt Figure

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Steinmetz, W. E.; Hickernell, F.; Mun, I. K.; Scharpen, L. H. J. Mol. Spectrosc. 1977, 68, 173-182.o

The microwave spectra of two conformers, trans and cis, of the title compound were recorded using two molecular beam Fourier transform microwave spectrometers operating in the frequency range 2 GHz to 40 GHz, and aimed at analysis of their ¹⁴N quadrupole hyperfine structures. Rotational constants, centrifugal distortion constants, and nuclear quadrupole coupling constants (NQCCs) χ_aa and χ_bb - χ_cc, were all determined with very high accuracy. Two fits including 176 and 117 hyperfine transitions were performed for the trans and cis conformers, respectively. Standard deviations of both fits are close to the measurement accuracy of 2 kHz. The NQCCs of the two conformers are almost exactly the same, and are compared with values found for other saturated and unsaturated formamides. Complementary quantum chemical calculations - MP2/6-311++G(d,p) rotational constants, MP2/cc-pVTZ centrifugal distortion constants, and B3PW91/6-311+G(d,p)//MP2/6-311++G(d,p) nuclear quadrupole coupling constants - give spectroscopic parameters in excellent agreement with the experimental parameters. B3PW91/6-311+G(d,p) calculated electric field gradients, in conjunction with eQ/h = 4.599(12) MHz/a.u., yields more reliable NQCCs for formamides possessing conjugated π-electron systems than does the B3PW91/6-311+G(df,pd) model recommended in Ref. W. C. Bailey, Chem. Phys., 2000, 252, 57. whereas this latter performs better for aliphatic formamides.W. C. Bailey, Calculation of Nuclear Quadrupole Coupling Constants in Gaseous State Molecules, http://nqcc.wcbailey.net/index.html.e conclude from this that f-polarization functions on heavy atoms hinder rather than help with modeling of conjugated π-electron systems.

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W. C. Bailey, Chem. Phys., 2000, 252, 57., W. C. Bailey, Calculation of Nuclear Quadrupole Coupling Constants in Gaseous State Molecules, http://nqcc.wcbailey.net/index.html.W

l0pt Figure Microwave spectroscopy has been restricted to the investigation of small molecules in the last years. However, with the advent of FTMW T. J. Balle and W. H. Flygare Rev. Sci. Instrum. 52, 33-45, 1981.^, J.−U. Grabow, W. Stahl and  H. Dreizler Rev. Sci. Instrum. 67, 4072−4084, 1996.nd CP−FTMW G. G. Brown, B. D. Dian,  K. O. Douglass, S. M. Geyer,  S. T. Shipman and B. H. Pate Rev. Sci. Instrum. 79, 0531031/1−053103/13, 2008.pectroscopies coupled with laser vaporization techniques E. J. Cocinero, A. Lesarri, P. Écija, F. J. Basterretxea, J. U. Grabow, J. A. Fernández and F. Castaño Angew. Chem. Int. Ed. 51, 3119−3124, 2012.t has turned into a very competitive methodology in the studies of moderate−size biomolecules.Here, we present the study of purine, characterized by two aromatic rings, one six− and one five−membered, fused together to give a planar aromatic bicycle. Biologically, it is the mainframe of two of the five nucleobases of DNA and RNA. Two tautomers were observed by FTMW spectroscopy coupled to UV ultrafast laser vaporization system. The population ratio of the two main tautomers [N(7)H]/[N(9)H] is about 1/40 in the gas phase. It contrasts with the solid state where only the N(7)H species is present, or in solution where a mixture of both tautomers is observed. For both species, a full quadrupolar hyperfine analysis has been performed. This has led to the determination of the full sets of diagonal quadrupole coupling constants of the four ^14 J.-U.Grabow, W.Stahl and H.Dreizler Rev. Sci. Instrum. 67, 4072-4084, 1996.aG.G.Brown, B.D.Dian, K.O.Douglass, S.M.Geyer, S.T.Shipman and B.H.Pate Rev. Sci. Instrum. 79, 0531031/1-053103/13, 2008.sE.J.Cocinero, A.Lesarri, P.cija, F.J.Basterretxea, J.U.Grabow, J.A.Fernndez and F. Castao Angew. Chem. Int. Ed. 51, 3119-3124, 2012.i

The microwave spectrum of the molecule bromoperfluoroacetone has been measured on a CP-FTMW spectrometer in the 6-18. The spectra is dense with approximately one transition every 5 MHz on average. Rotational constants, centrifugal distortion parameters, and nuclear quadrupole coupling constants will be discussed. Comparisons to the previously studied halogen analogues perfluoroacetoneJ.-U. Grabow, N. Heineking, and W. Stahl, Z. Naturforsch. 46a (1991) 229.nd chloroperfluoroacetoneG. Kadiwar, C. T. Dewberry, G. S. Grubbs II and S. A. Cooke, Talk RH11, 65^th International Symposium on Molecular Spectroscopy (2010).long with a family of previously studied halogenated acetone species will be discussed.

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J.-U. Grabow, N. Heineking, and W. Stahl, Z. Naturforsch. 46a (1991) 229.a G. Kadiwar, C. T. Dewberry, G. S. Grubbs II and S. A. Cooke, Talk RH11, 65^th International Symposium on Molecular Spectroscopy (2010).a

CF₂ClCCl₃ has recently been identified among several new ozone- depleting substances in the atmosphere.J.C.Laube, M.J.Newland, C.Hogan, et al., Nature Geoscience 7, 266 (2014).here are no literature reports concerning rotational spectroscopy of this molecule, although we were recently able to report its first chirped pulse, supersonic expansion spectrum.Z.Kisiel, E.Bia kowska-Jaworska, L.Pszczó kowski, I.Uriarte, P.Ejica, F.J.Basterretxea, E.J.Cocinero, 70^th ISMS, Champaign-Urbana, Illinois, RF-11 (2015).F₂ClCCl₃ has a rather small dipole moment so that the spectrum is weak and each transition displays very complex nuclear quadrupole hyperfine structure resulting from the presence of four chlorine nuclei. We have presently been able to carry out a complete analysis of the hyperfine structure by combining the information from chirped pulse spectra with dedicated higher resolution measurements made with a cavity supersonic expansion instrument. The hyperfine analysis was carried out with Pickett's SPFIT/SPCAT package and the sizes of Hamiltonian matrices are sufficiently large to require the use of 64-bit compilation of these programs (made available for both Windows and Linux systems on the PROSPE website). The resulting fit is to within experimental accuracy and is supported by ab initio calculations. The precise values of off-diagonal hyperfine constants for all nuclei lead to useful angular information that is complementary to direct structural information from moments of inertia.Z.Kisiel, E.Bia kowska-Jaworska, L.Pszczó kowski, J.Chem.Phys. 109, 10263 (1998).html:<hr /><h3>Footnotes: J.C.Laube, M.J.Newland, C.Hogan, et al., Nature Geoscience 7, 266 (2014).T Z.Kisiel, E.Bia kowska-Jaworska, L.Pszczó kowski, I.Uriarte, P.Ejica, F.J.Basterretxea, E.J.Cocinero, 70^th ISMS, Champaign-Urbana, Illinois, RF-11 (2015).C Z.Kisiel, E.Bia kowska-Jaworska, L.Pszczó kowski, J.Chem.Phys. 109, 10263 (1998).

The perturbative treatment of spin-orbit coupling (SOC) on top of scalar-relativistic calculations is a cost-effective alternative to rigorous fully relativistic calculations. In this work the applicability of the perturbative scheme in the framework of spin-free exact two-component theory is demonstrated with calculations of SO splittings and SOC contributions to molecular properties in small heavy-metal containing radicals, including AuO, AuS, and ThO⁺. The equation of motion coupled cluster techniques have been used to accurately account for the electron-correlation effects in these radicals, and basis-set effects are carefully analyzed. The computed results are compared with experimental measurements for SO splittings and dipole moments when available.

Like almost all astronomical studies, exoplanet investigations are observational endeavors that rely primarily on remote spectroscopic sensing to infer the physical properties of planets. Most exoplanet related information is inferred from to temporal variation of luminosity of the parent star. An effective method of monitoring this variation is via Magnetic Doppler Imaging (MDI)O. Kochukhov, N. Rusomarov, J. A. Valenti, H. C. Stempels, F. Snik, M. Rodenhuis, N. Piskunov, V. Makaganiuk, C. U. Keller and C. M. Johns-Krull, Astron. Astrophys. 574 (Pt. 2), A79/71-A79/12 (2015). which uses optical polarimetryS. V. Berdyugina, Astron. Soc. Pac. Conf. Ser. 437 (Solar Polarization 6), 219-235 (2011).f paramagnetic molecules or atoms. One promising paramagnetic stellar absorption is the near infrared spectrum of VOS. V. Berdyugina, P. A. Braun, D. M. Fluri and S. K. Solanki, Astron. Astrophys. 444 (3), 947-960 (2005). With this in mind, we have begun a project to record and analyze the field-free and Zeeman spectrum of the band. A cold (approx. 20 K) beam of VO was probed with a single frequency laser and detected using laser induced fluorescence. The determined spectral parameters will be discussed and compared to those extracted from the analysis of a hot spectrumA. S. C. Cheung, P. G. Hajigeorgiou, G. Huang, S. Z. Huang and A. J. Merer, J. Mol. Spectrosc. 163 (2), 443-458 (1994).

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O. Kochukhov, N. Rusomarov, J. A. Valenti, H. C. Stempels, F. Snik, M. Rodenhuis, N. Piskunov, V. Makaganiuk, C. U. Keller and C. M. Johns-Krull, Astron. Astrophys. 574 (Pt. 2), A79/71-A79/12 (2015)., S. V. Berdyugina, Astron. Soc. Pac. Conf. Ser. 437 (Solar Polarization 6), 219-235 (2011).o S. V. Berdyugina, P. A. Braun, D. M. Fluri and S. K. Solanki, Astron. Astrophys. 444 (3), 947-960 (2005).. A. S. C. Cheung, P. G. Hajigeorgiou, G. Huang, S. Z. Huang and A. J. Merer, J. Mol. Spectrosc. 163 (2), 443-458 (1994)..

Gold-sulfur and gold-oxygen bonds are key components to numerous established and emerging technologies that have applications as far ranging as medical imaging, catalysis, electronics, and material science. A major theoretical challenge for describing this bonding is correctly accounting for the large relativistic and electron correlation effects. Such effects are best studied in diatomic, AuX, molecules. Recently, the observed AuS electronic state energy ordering was measured and compared to a simple molecular orbital diagram predictionD. L. Kokkin, R. Zhang, T. C. Steimle, I. A. Wyse, B. W. Pearlman and T. D. Varberg, J. Phys. Chem. A., 119(48), 4412, 2015. Here we more thoroughly investigate the nature of the electronic states of both AuS and AuO from the analysis of high-resolution (FWHM ≅ 35MHz) optical Zeeman spectroscopy of the (0,0)B²Σ⁻−X²Π_3/2 bands. The determined fine and hyperfine parameters for the B²Σ⁻ state of AuO differ from those extracted from the analysis of a hot, Doppler-limited, spectrumL. C. O'Brien, B. A. Borchert, A. Farquhar, S. Shaji, J. J. O'Brien and R. W. Field, J. Mol. Spectrosc., 252(2), 136, 2008. It is demonstrated that the nature of the B²Σ⁻ states of AuO and AuS are radically different. The magnetic tuning of AuO and AuS indicates that the B²Σ⁻ states are heavily contaminated. D. L. Kokkin, R. Zhang, T. C. Steimle, I. A. Wyse, B. W. Pearlman and T. D. Varberg, J. Phys. Chem. A., 119(48), 4412, 2015.. L. C. O'Brien, B. A. Borchert, A. Farquhar, S. Shaji, J. J. O'Brien and R. W. Field, J. Mol. Spectrosc., 252(2), 136, 2008..

Sub-Doppler, saturation dip, measurements of transitions in the ν₁ + ν₃ band of ¹⁴NH₃ have been made by frequency comb-referenced diode laser absorption spectroscopy. The observed spectra exhibit either resolved or partially-resolved hyperfine splittings that are primarily determined by the ¹⁴N quadrupole coupling in the molecule. Modeling of the line shapes based on the known hyperfine level structure of the ground state of the molecule shows that, in nearly all cases, the upper state level has splittings similar to that of the same rotational level in the ground state. The data provide accurate frequencies for the line positions and the observed hyperfine splittings can be used to make or confirm rotational assignments. Of all the measurements, one transition, ^pP(5,4)_a at 195 994.73457 GHz, exhibits hyperfine structure which does not conform to that expected based on extrapolation from the known lower state hyperfine splittings. Examination of the known vibration-rotation level structure near the upper state energy shows that there exists a near degeneracy between this level and one in the ν₁ + 2ν₄ manifold which is of the appropriate symmetry to be mixed by magnetic hyperfine terms that couple ortho- and para- modifications of the molecule. It is possible that the unusual hyperfine splittings are a consequence of ortho-paro mixing, which has been predicted, but not previously seen in ammonia and further experimental measurements to investigate this possibility are ongoing. Acknowledgments: Work at Brookhaven National Laboratory was carried out under Contract No. DE-SC0012704 with the U.S. Department of Energy, Office of Science, and supported by its Division of Chemical Sciences, Geosciences and Biosciences within the Office of Basic Energy Sciences.

The determination of hyperfine parameters (quadrupole-coupling, spin-spin coupling, and spin-rotation constants) is one of the aims of high-resolution rotational spectroscopy. These parameters are relevant not only from a spectroscopic point of view, but also from a physical and/or chemical viewpoint, as they might provide detailed information on the chemical bond, structure, etc. In addition, the hyperfine structure of rotational spectra is so characteristic that its analysis may help in assigning the spectra of unknown species. In astronomical observations, hyperfine structures of rotational spectra would allow us to gain information on column densities and kinematics, and the omission of taking them into account can lead to a misinterpretation of the line width of the molecular emission lines. Nevertheless, the experimental determination of hyperfine constants can be a challenge not only for actual problems in resolving hyperfine structures themselves, but also due to the lack of reliable estimates or the complexity of the hyperfine structure itself. It is thus important to be able to rely on good predictions for such parameters, which can nowadays be provided by quantum-chemical calculations. In fact, the fruitful interplay of experiment and theory will be demonstrated by means of two study cases: the hypefine structure of the rotational spectra of HDS and ND₃. From an experimental point of view, the Lamb-dip technique has been employed to improve the resolving power in themillimeter- and submillimeterwave frequency range by at least one order of magnitude, thus making it possible to perform sub-Doppler measurements as well as to resolve narrow hyperfine structures. Concerning theory, it will be demonstrated that high-level calculations can provide quantitative estimates for hyperfine parameters (quadrupole coupling constants, spin-rotation tensors, spin-spin couplings, etc.) and shown how theoretical predictions are often essential for a detailed analysis of the hyperfine structure of the recorded spectra.