Adam M Daly

Universidad de Valladolid, Valladolid, Castille and León, Spain

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Publications (29)89.4 Total impact

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    ABSTRACT: New laboratory data of CH$_2$CHCN (vinyl cyanide) in its ground and vibrationally excited states at the microwave to THz domain allow searching for these excited state transitions in the Orion-KL line survey. Frequency-modulated spectrometers combined into a single broadband 50-1900 GHz spectrum provided measurements of CH$_2$CHCN covering a spectral range of 18-1893 GHz, whose assignments was confirmed by Stark modulation spectra in the 18-40 GHz region and by ab-initio anharmonic force field calculations. For analyzing the emission lines of CH$_2$CHCN species detected in Orion-KL we used the excitation and radiative transfer code (MADEX) at LTE conditions. The rotational transitions of the ground state of this molecule emerge from four cloud components of hot core nature which trace the physical and chemical conditions of high mass star forming regions in the Orion-KL Nebula. The total column density of CH$_2$CHCN in the ground state is (3.0$\pm$0.9)x10$^{15}$ cm$^{-2}$. We report on the first interstellar detection of transitions in the v10=1/(v11=1,v15=1) dyad in space, and in the v11=2 and v11=3 states in Orion-KL. The lowest energy vibrationally excited states of vinyl cyanide such as v11=1 (at 328.5 K), v15=1 (at 478.6 K), v11=2 (at 657.8 K), the v10=1/(v11=1,v15=1) dyad (at 806.4/809.9 K), and v11=3 (at 987.9 K) are populated under warm and dense conditions, so they probe the hottest parts of the Orion-KL source. Column density and rotational and vibrational temperatures for CH$_2$CHCN in their ground and excited states, as well as for the isotopologues, have been constrained by means of a sample of more than 1000 lines in this survey. Moreover, we present the detection of methyl isocyanide (CH$_3$NC) for the first time in Orion-KL and a tentative detection of vinyl isocyanide (CH$_2$CHNC) and give column density ratios between the cyanide and isocyanide isomers.
    07/2014;
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    ABSTRACT: New laboratory data of ethyl mercaptan, CH$_{3}$CH$_{2}$SH, in the millimeter and submillimeter-wave domains (up to 880 GHz) provided very precise values of the spectroscopic constants that allowed the detection of $gauche$-CH$_3$CH$_2$SH towards Orion KL. 77 unblended or slightly blended lines plus no missing transitions in the range 80-280 GHz support this identification. A detection of methyl mercaptan, CH$_{3}$SH, in the spectral survey of Orion KL is reported as well. Our column density results indicate that methyl mercaptan is $\simeq$ 5 times more abundant than ethyl mercaptan in the hot core of Orion KL.
    The Astrophysical Journal Letters 01/2014; 784(1). · 6.35 Impact Factor
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    ABSTRACT: A non-conventional vaporization method, using laser ablation of solid NaCl doped with d-erythrose, has been used to bring this sugar into the gas phase for rotational study. The jet cooled rotational spectrum of this C4 monosaccharide reveals the existence of two furanose forms, one α envelope and one β twist. Cooperative hydrogen bond networks and the anomeric effect have been found to be the main stabilization factors of the detected structures.
    Chemical Communications 10/2013; · 6.38 Impact Factor
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    ABSTRACT: Crystalline samples of d-xylose have been vaporized by laser ablation and probed in the gas phase using Fourier transform microwave spectroscopy. The rotational spectrum revealed the existence of two α-d-xylopyranose conformers stabilized by the anomeric effect and cooperative hydrogen bond networks. The experiment spectroscopically tracked fine structural changes upon clockwise and counterclockwise arrangements of the OH groups in the observed conformers. The five monosubstituted (13)C species of the most abundant conformer cc-α-(4)C1 have also been observed in their natural abundance, and its structure has been derived. This work demonstrates the pivotal role that the intramolecular hydrogen-bonding network plays in the conformational behavior of free monosaccharides.
    Physical Chemistry Chemical Physics 09/2013; · 3.83 Impact Factor
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    ABSTRACT: A clear picture of the conformations of isolated 2-deoxy-D-ribose was obtained using chirped pulse and Balle–Flygare Fourier-transform microwave spectrometers, both coupled with laser ablation sources. Two conformers of α-D-deoxyribopyranose and four of β-D-deoxyribopyranose were found on the basis of the spectroscopic rotational parameters and ab initio predictions. The substitution and effective structures of the most abundant conformer have been determined.
    Angewandte Chemie International Edition 09/2013; · 11.34 Impact Factor
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    ABSTRACT: Two conformers of D-fructopyranose are characterized using laser ablation and broadband Fourier-transform microwave spectroscopy. Both species are stabilized by complicated intramolecular hydrogen-bonding networks. Structural motifs related to the sweetness of D-fructopyranose are revealed for the most stable conformer.
    ChemPhysChem 02/2013; · 3.35 Impact Factor
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    ABSTRACT: Microwave spectroscopy has been applied to characterize the conformations adopted in the gas phase by a small peptide derived from alanine, N-acetyl-L-alaninamide (Ac-Ala-NH2). This compound was vaporized by laser ablation and shown to exist as a mixture of Ceq7 and C5 conformers stabilized by a COHN intramolecular hydrogen bond closing a seven- or a five-membered ring, respectively. The complicated quadrupole hyperfine structure originated from two 14N nuclei has been completely resolved for both species and the derived nuclear quadrupole coupling constants have been used to determine the Ramachandran angles that describe their molecular shapes.
    Physical Chemistry Chemical Physics 01/2013; 15(7). · 3.83 Impact Factor
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    ABSTRACT: Microwave spectroscopy has been applied to characterize the conformations adopted in the gas phase by a small peptide derived from alanine, N-acetyl-l-alaninamide (Ac-Ala-NH(2)). This compound was vaporized by laser ablation and shown to exist as a mixture of C and C(5) conformers stabilized by a COHN intramolecular hydrogen bond closing a seven- or a five-membered ring, respectively. The complicated quadrupole hyperfine structure originated from two (14)N nuclei has been completely resolved for both species and the derived nuclear quadrupole coupling constants have been used to determine the Ramachandran angles that describe their molecular shapes.
    Physical Chemistry Chemical Physics 01/2013; · 3.83 Impact Factor
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    ABSTRACT: Ethyl cyanide, CH 3 CH 2 CN, is an important interstellar molecule with a very dense rotational-vibrational spectrum. On the basis of new laboratory data in the range of 17-605 GHz and ab initio calculations, two new vibrational states, ν 12 and ν 20 , have been detected in molecular clouds of Orion. Laboratory data consist of Stark spectroscopy (17-110 GHz) and frequency-modulated spectrometers (GEM laboratory in Valladolid: 17-170, 270-360 GHz; Toyama: 26-200 GHz; Emory: 200-240 GHz; Ohio State: 258-368 GHz; and JPL: 270-318, 395-605 GHz). More than 700 distinct lines of each species were measured in J up to 71 and in K a up to 25. The states were fitted with Watson's S-reduction Hamiltonian. The two new states have been identified in the interstellar medium toward the Orion Nebula (Orion KL). The ground state, the isotopologues of CH 3 CH 2 CN, and the vibrationally excited states have been fitted to obtain column densities and to derive vibrational temperatures. All together, ethyl cyanide is responsible for more than 2000 lines in the observed frequency range of 80-280 GHz.
    The Astrophysical Journal 01/2013; 768:81. · 6.73 Impact Factor
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    ABSTRACT: The millimeter wave spectra of phenol in the vibrational ground state and the first excited states of the bending and torsion vibrational modes have been studied in the frequency regions of 140–170 GHz and 280–360 GHz. The internal rotation of the hydroxyl group is responsible for the observed tunneling splitting into two substates (vt, vb)+ and (vt, vb)− and more than 3500 distinct tunneling–rotational bR- and bQ-type transitions between them were measured and analyzed. Furthermore, accidental near degeneracies of the (±) and (−) energy levels were observed in case of the ground state and the vb = 1 excited state and the analysis using a two-state effective Hamiltonian including tunneling–rotational Coriolis-like terms was performed. The analysis of the microwave data provided very precise values of the spectroscopic constants necessary for the astrophysical search of phenol. We report a tentative detection for this molecule in the IRAM 30m line survey of Orion KL.
    Journal of Molecular Spectroscopy 01/2013; 289:13 - 20. · 1.67 Impact Factor
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    ABSTRACT: Fast-passage Fourier transform microwave spectroscopy in combination with a laser ablation source has been successfully applied to probe vitamin C (l-ascorbic acid) in the gas phase. Its ethyldiol side chain and two hydroxyl groups around the γ-lactone ring provide five internal rotation axes, enabling vitamin C to assume a wide variety of nonplanar 3D cooperative hydrogen bond networks that can also include the keto and ether functions. The rotational constants extracted from the analysis of the spectrum unequivocally identify the existence of three dominant conformers stabilized by different intramolecular hydrogen bonding motifs forming five-, six-, or seven-membered rings.
    Journal of Physical Chemistry Letters 01/2013; 4(1):65-69. · 6.59 Impact Factor
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    ABSTRACT: Ein klares Bild von den Konformationen isolierter 2‐Deoxy‐D‐ribose wurde mithilfe von Chirped‐Puls‐ und Balle‐Flygare‐Fourier‐Transformations‐Mikrowellenspektrometrie jeweils in Kombination mit Laserablationsquellen erhalten. Zwei Konformere der α‐D‐Deoxyribopyranose und vier der β‐D‐Deoxyribopyranose wurden auf Basis der spektroskopischen Rotationsparameter und von Ab‐initio‐Rechnungen identifiziert. Das Substitutionsmuster und die effektiven Strukturen der häufigsten Konformere wurden bestimmt.
    Angewandte Chemie 01/2013; 125(45).
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    ABSTRACT: The microwave spectrum of AsP3 has been measured and assignments for three different vibrational states have been made. The symmetric top ΔJ = +1 transitions have been fit to obtain rotational constants, centrifugal distortion constants and quadrupole coupling strengths for the three vibrational states (I–III), BI = 2201.394(1) MHz, eQqaaI = 48.728(5) MHz, DJI = 0.2(3) kHz, DJKI = 0.5(1) kHz and σI = 4 kHz, BII = 2192.26(1) MHz, eQqaaII = 48.62(4) MHz, BIII = 2183.93(2) MHz, eQqaaIII = 48.53(4) MHz. The experimental vibration–rotation coupling constant, α(ν4) = 9.20(3) MHz is compared with results from MP2/6-311G** calculations. The excited states (II and III) are tentatively assigned to the ν4 and 2ν4 excited vibrational states.
    Journal of Molecular Spectroscopy 08/2012; 278:68–71. · 1.67 Impact Factor
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    ABSTRACT: Using a combination of laser ablation and jet cooled FT-MW spectroscopy the pure rotational spectrum of AlCCH and AgCCH in the (X1Σ+) electronic ground state has been recorded and assigned in the 6–20 GHz region. A newly constructed ablation-discharge source has been coupled to our LA-MB-FTMW spectrometer and tested as a generator of metal acetylides. Laser ablation of the pure metal has been demonstrated as a very efficient method to create unstable compounds in the gas phase. The high spectral resolution of our instrument provided an accurate set of rotational, quadrupole (only for AlCCH) and centrifugal distortion constants which are reported for the first time.
    Journal of Molecular Spectroscopy 01/2012; 278:31 - 34. · 1.67 Impact Factor
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    ABSTRACT: The microwave spectrum for N-hydroxypyridine-2(1H)-thione (pyrithione) was measured in the frequency range 6-18 GHz, providing accurate rotational constants and nitrogen quadrupole coupling strengths for three isotopologues, C(5)H(4)(32)S(14)NOH, C(5)H(4)(32)S(14)NOD, and C(5)H(4)(34)S(14)NOH. Pyrithione was found to be in a higher concentration in the gas phase than the other tautomer, 2-mercaptopyridine-N-oxide (MPO). Microwave spectroscopy is best suited to determine which structure predominates in the gas phase. The measured rotational constants were used to accurately determine the coordinates of the substituted atoms and provided sufficient data to determine some of the important structural parameters for pyrithione, the only tautomer observed in the present work. The spectra were obtained using a pulsed-beam Fourier transform microwave spectrometer, with sufficient resolution to allow accurate measurements of the (14)N nuclear quadrupole hyperfine interactions. Ab initio calculations provided structural parameters and quadrupole coupling strengths that are in very good agreement with measured values. The experimental rotational constants for the parent compound are A = 3212.10(1), B = 1609.328(7), and C = 1072.208(6) MHz, yielding the inertial defect Δ(0) = -0.023 amu·Å(2) for the C(5)H(4)(32)S(14)NOH isotopologue. The observed near zero inertial defect clearly indicates a planar structure. The least-squares fit structural analysis yielded the experimental bond lengths R(O-H) = 0.93(2) Å, R(C-S) = 1.66(2) Å, and angle (N-O-H) = 105(4)° for the ground state structure.
    The Journal of Physical Chemistry A 11/2011; 115(50):14526-30. · 2.77 Impact Factor
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    ABSTRACT: Microwave spectra of the propiolic acid–formic acid doubly hydrogen bonded complex were measured in the 1 GHz to 21 GHz range using four different Fourier transform spectrometers. Rotational spectra for seven isotopologues were obtained. For the parent isotopologue, a total of 138 a-dipole transitions and 28 b-dipole transitions were measured for which the a-dipole transitions exhibited splittings of a few MHz into pairs of lines and the b-type dipole transitions were split by ∼580 MHz. The transitions assigned to this complex were fit to obtain rotational and distortion constants for both tunneling levels: A0+ = 6005.289(8), B0+ = 930.553(8), C0+ = 803.9948(6) MHz, Δ0+J = 0.075(1), Δ0+JK = 0.71(1), and δ0+j = −0.010(1) kHz and A0− = 6005.275(8), B0− = 930.546(8), C0− = 803.9907(5) MHz, Δ0−J = 0.076(1), Δ0−JK = 0.70(2), and δ0−j = −0.008(1) kHz. Double resonance experiments were used on some transitions to verify assignments and to obtain splittings for cases when the b-dipole transitions were difficult to measure. The experimental difference in energy between the two tunneling states is 291.428(5) MHz for proton-proton exchange and 3.35(2) MHz for the deuterium-deuterium exchange. The vibration-rotation coupling constant between the two levels, Fab, is 120.7(2) MHz for the proton-proton exchange. With one deuterium atom substituted in either of the hydrogen-bonding protons, the tunneling splittings were not observed for a-dipole transitions, supporting the assignment of the splitting to the concerted proton tunneling motion. The spectra were obtained using three Flygare-Balle type spectrometers and one chirped-pulse machine at the University of Virginia. Rotational constants and centrifugal distortion constants were obtained for HCOOH···HOOCCCH, H13COOH···HOOCCCH, HCOOD···HOOCCCH, HCOOH···DOOCCCH, HCOOD···DOOCCCH, DCOOH···HOOCCCH, and DCOOD···HOOCCCH. High-level ab initio calculations provided initial rotational constants for the complex, structural parameters, and some details of the proton tunneling potential energy surface. A least squares fit to the isotopic data reveals a planar structure that is slightly asymmetric in the OH distances. The formic OH···O propiolic hydrogen bond length is 1.8 Å and the propiolic OH···O formic hydrogen bond length is 1.6 Å, for the equilibrium configuration. The magnitude of the dipole moment was experimentally determined to be 1.95(3) × 10−30 C m (0.584(8) D) for the 0+ states and 1.92(5) × 10−30 C m (0.576(14) D) for the 0− states.
    The Journal of Chemical Physics 10/2011; 135(15):154304-154304-12. · 3.12 Impact Factor
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    ABSTRACT: Microwave spectra of 1-d-(η7-cycloheptatriene)48Ti(η5-cyclopentadienyl) (CHT–Ti–Cp) and two singly substituted 13C isotopomers were measured and gas phase structural parameters were determined. Rotational transitions were also measured for (η7-cycloheptatriene)52Cr(η5-cyclopentadienyl). Rotational constants for the Ti complex were found to be A=1720(4)MHz, B=769.269(1)MHz and C=766.131(1)MHz and for [13CC6H7–48Ti–C5H5], A=1773(2)MHz, B=769.6931(4)MHz and C=761.1789(5)MHz and for [1-d-C7H648TiC5H5] and A=1270(5)MHz, B=767.0142(9)MHz and C=765.323(1)MHz for [C7H748Ti13CC4H5]. A structural analysis for the (CHT–Ti–Cp) data showed that the cycloheptatriene ring protons droop towards titanium as predicted by DFT and MP2 calculations. The droop of the protons toward the metal was experimentally determined to be 8.0(2)° out of the plane of the cycloheptatriene ring. The ring center distance to titanium was found to be 2.01(3)Å for Ti–Cp and 1.48(3)Å for Ti–CHT using a least squares fit to the measured rotational constants and fixing many of the structural parameters to the calculated values. The spectrum of the normal isotopomer (η7-cycloheptatriene)Ti(η5-cyclopentadienyl) was re-measured and a discussion of the possible 47Ti quadrupole coupling constants is presented. The chromium analog K=0 spectrum was analyzed to obtain B=851.229MHz, and DJ=0.028(6)kHz. Results from structure calculations are reported and discussed for (CHT–M–Cp) complexes with M=Ti, Cr, Zr, Hf, Mo, W using MP2, B3PW91 and B3LYP methods.
    North-Holland Series in Applied Mathematics and Mechanics 01/2011; 267(1):172-177.
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    ABSTRACT: The rotational spectra for six isotopologues of the complex formed between formamide and formic acid have been measured using a pulsed-beam Fourier transform microwave spectrometer and analyzed to obtain rotational constants and quadrupole coupling parameters. The rotational constants and quadrupole coupling strengths obtained for H  (12)COOH-H(2)  (14)NCOH are A = 5889.465(2), B = 2148.7409(7), 1575.1234(6), eQq(aa) = 1.014(5), eQq(bb) = 1.99(1), and eQq(cc) = -3.00(1) MHz. Using the 15 rotational constants obtained for the H  (13)COOH, HCOOD, DCOOH, and H(2)  (15)NCHO isotopologues, key structural parameters were obtained from a least-squares structure fit. Hydrogen bond distances of 1.78 Å for R(O3⋯H1) and 1.79 Å for R(H4⋯O1) were obtained. The "best fit" value for the angle(C-O-H) of formic acid is significantly larger than the monomer value of 106.9° with an optimum value of 121.7(3)°. The complex is nearly planar with inertial defect Δ = -0.158 amu  Å(2). The formamide proton is moved out of the molecular plane by 15(3)° for the best fit structure. Density functional theory using B3PW91, HCTH407, and TPSS as well as MP2 and CCSD calculations were performed using 6-311++G(d,p) and the results were compared to experimentally determined parameters.
    The Journal of Chemical Physics 11/2010; 133(17):174304. · 3.12 Impact Factor
  • The Journal of Chemical Physics 08/2010; 133(7):079903. · 3.12 Impact Factor
  • Adam M. Daly, Stephen G. Kukolich
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    ABSTRACT: The microwave spectrum of the gas phase complex formed between propiolic acid (HCCCOOH) and formic acid (HCOOH) along with 5 other isotopomers were obtained using a pulsed beam fourier transform microwave spectrometer. The spectra of the HC12OOH and HC13OOH isotopomers were each fit to two sets of rotational constants. The parent rotational constants were 5988.7(8), 927.782(7), 803.720(7) and 5988(1), 927.779(9) 804.058(9) MHz respectively. Isotomers containing deuterium in the OH bonds, HCOOD and HCCCOOD, do not show this feature. We tentatively assign the two sets of rotational constants to the two different inversion states for the concerted proton tunnelling in the hydrogen bonds.
    06/2010;

Publication Stats

61 Citations
89.40 Total Impact Points

Institutions

  • 2012–2014
    • Universidad de Valladolid
      • Facultad de Ciencias
      Valladolid, Castille and León, Spain
  • 2008–2012
    • The University of Arizona
      • Department of Chemistry and Biochemistry (College of Science)
      Tucson, Arizona, United States