2010 ASTROMOL Publications


[1] Warm water vapour in the sooty outflow from a luminous carbon star
Decin, L.; Agúndez, M.; Barlow, M.J.; Daniel, F.; Cernicharo, J. & 32 co-authors
Nature
467; 64 – 67; 09/2010
36.101
The detection in 2001 of circumstellar water vapour around the ageing carbon star IRC +10216 challenged the current understanding of chemistry in old stars, because water was predicted to be almost absent in carbon-rich stars. Here, it is reported the detection of dozens of water vapour lines in the far-infrared and sub-millimetre spectrum of IRC +10216 using the Herschel satellite. This includes some high-excitation lines with energies corresponding to ~1,000K, which can be explained only if water is present in the warm inner sooty region of the envelope


[2] Photochemistry in the Inner Layers of Clumpy Circumstellar Envelopes: Formation of Water in C-rich Objects and of C-bearing Molecules in O-rich Objects
Agúndez, M.; Cernicharo, J.; Guelin, M.
The Astrophysical Journal
724; L133; 12/2010
7.436
A mechanism based on the penetration of interstellar ultraviolet photons into the inner layers of clumpy circumstellar envelopes (CSEs) around asymptotic giant branch stars is proposed to explain the non-equilibrium chemistry observed in such objects. The proposed mechanism would explain the recent observation of warm water vapor in the carbon-rich envelope IRC+10216 with the Herschel Space Observatory and predict that H2O should be detectable in other carbon-rich objects


[3] A line confusion limited millimeter survey of Orion KL . I. Sulfur carbon chains
Tercero, B.; Cernicharo, J.; Pardo, J. R.; Goicoechea, J. R.
Astronomy and Astrophysics
517; 96; 07/2010
4.179
We perform a sensitive (line confusion limited), single-side band spectral survey towards Orion KL with the IRAM 30 m telescope, covering the following frequency ranges: 80–115.5 GHz, 130–178 GHz, and 197–281 GHz. We detect more than 14?400 spectral features of which 10?040 have been identified up to date and attributed to 43 different molecules, including 148 isotopologues and lines from vibrationally excited states. In this paper, we focus on the study of OCS, HCS+, H2CS, CS, CCS, C3S, and their isotopologues. We report the first detection of OCS ?2 = 1 and ?3 = 1 vibrationally excited states in space and the first detection of C3S in warm clouds.


[4] Astronomical identification of CN, the smallest observed molecular anion
Agúndez, M.; Cernicharo, J.; Guélin, M.; Kahane, C.; Roueff, E.; K?os, J.; Aoiz, F. J.; and 7 coauthors
Astronomy and Astrophysics
517; L2; 07/2010
4.179
We present the first astronomical detection of a diatomic negative ion, the cyanide anion CN, and quantum mechanical calculations of the excitation of this anion by means of collisions with para-H2. The anion CN is identified by observing the J = 2-1 and J = 3-2 rotational transitions in the C-star envelope IRC +10216 with the IRAM 30-m telescope


[5] Herschel-PACS spectroscopy of the intermediate mass protostar NGC 7129 FIRS 2
Fich, M.; Johnstone, D.; van Kempen, T. A.; McCoey, C.; Fuente, A.; and 56 co-authors
Astronomy and Astrophysics
518; L86; 07/2010
4.179
We present preliminary results of the first Herschel spectroscopic observations of NGC 7129 FIRS2, an intermediate mass star-forming region. We attempt to interpret the observations in the framework of an in-falling spherical envelope. Virtually all of this high excitation emission must arise in structures such as as along the walls of the outflow cavity with the emission produced by a combination of UV photon heating and/or non-dissociative shocks


[6] The 35Cl/37Cl isotopic ratio in dense molecular clouds: HIFI observations of hydrogen chloride towards W3 A
Cernicharo, J.; Goicoechea, J. R.; Daniel, F.; Agúndez, M.; Caux, E.; de Graauw, T.; and 6 co-authors
Astronomy and Astrophysics
518; L115; 07/2010
4.179
We report on the detection with the HIFI instrument on board the Herschel satellite of the two hydrogen chloride isotopologues, H35Cl and H37Cl, towards the massive star-forming region W3 A


[7] Detection of anhydrous hydrochloric acid, HCl, in IRC +10216 with the Herschel SPIRE and PACS spectrometers . Detection of HCl in IRC +10216
Cernicharo, J.; Decin, L.; Barlow, M. J.; Agúndez, M.; and 31 co-authors
Astronomy and Astrophysics
518; L136; 07/2010
4.179
We report on the detection of anhydrous hydrochloric acid (hydrogen chlorine, HCl) in the carbon-rich star IRC +10216 using the spectroscopic facilities onboard the Herschel satellite


[8] Herschel-SPIRE FTS spectroscopy of the carbon-rich objects AFGL 2688, AFGL 618, and NGC 7027
Wesson, R.; Cernicharo, J.; Barlow, M. J.; Matsuura, M.; and 21 co-authors
Astronomy and Astrophysics
518: L144; 07/2010
4.179
We detect water in AFGL 2688 for the first time, and confirm its presence in AFGL 618 in both ortho and para forms. In addition, we report the detection of the J = 1-0 line of CH+ in NGC 7027.


[9] Waves on the surface of the Orion molecular cloud
Berné, O.; Marcelino, N.; Cernicharo, J.
Nature
466; 947-949; 08/2010
36.101
Here we report the presence of waves at the surface of the Orion molecular cloud near where massive stars are forming. The waves seem to be a Kelvin-Helmholtz instability that arises during the expansion of the nebula as gas heated and ionized by massive stars is blown over pre-existing molecular gas.


[10] Herschel/HIFI observations of high-J CO transitions in the protoplanetary nebula CRL 618
Bujarrabal, V.; Alcolea, J.; Soria-Ruiz, R.; Planesas, P.; Teyssier, D.; Marston, A. P.; Cernicharo, J.; and 21 co-authors
Astronomy and Astrophysics
521; L3; 10/2010
4.179
The 12CO J = 16-15, 10-9, and 6-5 lines are easily detected in this source. Both 13CO J = 10-9 and 6-5 are also detected. Wide profiles showing spectacular line wings have been found, particularly in 12CO J = 16-15. Other lines observed simultaneously with CO are also shown.


[11] Water content and wind acceleration in the envelope around the oxygen-rich AGB star IK Tauri as seen by Herschel/HIFI
Decin, L.; Justtanont, K.; De Beck, E.; Lombaert, R.; de Koter, A.; and 23 co-authors
Astronomy and Astrophysics
521; L4; 10/2010
4.179
We report on the first detection of H216O and the rarer isotopologues H217O and H218O in both the ortho and para states. We deduce a total water content (relative to molecular hydrogen) of 6.6 × 10-5, and an ortho-to-para ratio of 3:1. These results are consistent with the formation of H2O in thermodynamical chemical equilibrium at photospheric temperatures, and does not require pulsationally induced non-equilibrium chemistry, vaporization of icy bodies or grain surface reactions.


[12] Discovery of water vapour in the carbon star V Cygni from observations with Herschel/HIFI
Neufeld, D. A.; González-Alfonso, E.; Melnick, G.; Pu?ecka, M.; Schmidt, M.; Szczerba, R.; Bujarrabal, V.; Alcolea, J.; Cernicharo, J.; and 19 co-authors
Astronomy and Astrophysics
521; L5; 10/2010
4.179
We report the discovery of water vapour toward the carbon star V Cygni. This detection of thermal water vapour emission, carried out as part of a small survey of water in carbon-rich stars, is only the second such detection toward a carbon-rich AGB star, the first having been obtained by the Submillimeter Wave Astronomy Satellite toward IRC+10216.


[13] A HIFI preview of warm molecular gas around ? Cygni: first detection of H2O emission toward an S-type AGB star
Justtanont, K.; Decin, L.; Schöier, F. L.; Maercker, M.; Olofsson, H.; Bujarrabal, V.; and 21 co-authors
Astronomy and Astrophysics
521; L6; 10/2010
4.179
We report the first detection of circumstellar H2O rotational emission lines in an S-star. Using the high-J CO lines to derive the parameters for the circumstellar envelope, we modelled both the ortho- and para-H2O lines. Our modelling results are consistent with the velocity structure expected for a dust-driven wind.


[14] Herschel/HIFI deepens the circumstellar NH3 enigma
Menten, K. M.; Wyrowski, F.; Alcolea, J.; De Beck, E.; Decin, L.; Marston, A. P.; Bujarrabal, V.; Cernicharo, J.; and 18
Astronomy and Astrophysics
521; L7; 10/2010
4.179
Circumstellar envelopes (CSEs) of a variety of evolved stars have been found to contain ammonia (NH3) in amounts that exceed predictions from conventional chemical models by many orders of magnitude. While our radiative transfer modeling does not yield satisfactory fits to the observed line profiles, it does lead to abundance estimates that confirm the very high values found in earlier studies. New ways to tackle this mystery will include further Herschel observations of more NH3 lines and imaging with the Expanded Very Large Array


[15] A high-resolution line survey of IRC +10216 with Herschel/HIFI. First results: Detection of warm silicon dicarbide (SiC2)
Cernicharo, J.; Waters, L. B. F. M.; Decin, L.; Encrenaz, P.; Tielens, A. G. G. M.; Agúndez, M.; and 21 co-authors
Astronomy and Astrophysics
521; L8; 10/2010
4.179
We present the first results of a high-spectral-resolution survey of the carbon-rich evolved star IRC+10216 that was carried out with the HIFI spectrometer onboard Herschel. We identified 55 SiC2 transitions involving energy levels between 300 and 900 K. By analysing these rotational lines, we conclude that SiC2 is produced in the inner dust formation zone


[16] Excitation and abundance of C3 in star forming cores. Herschel/HIFI observations of the sight-lines to W31C and W49N
Mookerjea, B.; Giesen, T.; Stutzki, J.; Cernicharo, J.; Goicoechea, J. R.; and 46 co-authors
Astronomy and Astrophysics
521; L13; 10/2010
4.179
We present spectrally resolved observations of triatomic carbon (C3) in several ro-vibrational transitions between the vibrational ground state and the low-energy ?2 bending mode at frequencies between 1654-1897 GHz along the sight-lines to the submillimeter continuum sources W31C and W49N, using Herschel HIFI instrument. We detect C3 in absorption arising from the warm envelope surrounding the hot core, as indicated by the velocity peak position and shape of the line profile.


[17] Interstellar CH absorption in the diffuse interstellar medium along the sight-lines to G10.6-0.4 (W31C), W49N, and W51
Gerin, M.; de Luca, M.; Goicoechea, J. R.; Herbst, E.; Falgarone, E.; Godard, B.; Bell, T. A.; and 51 co-authors
Astronomy and Astrophysics
521; L16; 10/2010
4.179
We report the detection of the ground state N,J = 1,3/2 ? 1,1/2 doublet of the methylidyne radical CH at ~532 GHz and ~536 GHz with the Herschel/HIFI instrument along the sight-line to the massive star-forming regions G10.6-0.4 (W31C), W49N, and W51. We propose that CCH can be used as another tracer of the molecular gas in the absence of better tracers


[18] Herschel observations in the ultracompact HII region Mon R2. Water in dense photon-dominated regions (PDRs)
Fuente, A.; Berné, O.; Cernicharo, J.; Rizzo, J. R.; González-García, M.; Goicoechea, J. R.; Pilleri, P.; and 38 co-authors
Astronomy and Astrophysics
521; L23; 10/2010
4.179
Monoceros R2, at a distance of 830 pc, is the only ultracompact H ii region (UC H ii) where the photon-dominated region (PDR) between the ionized gas and the molecular cloud can be resolved with Herschel. We determine an ortho-water abundance of ?2 × 10-8 in Mon R2. Because shocks are unimportant in this region and our estimate is based on H218O observations that avoids opacity problems, this is probably the most accurate estimate of the water abundance in PDRs thus far.


[19] Herschel/HIFI spectroscopy of the intermediate mass protostar NGC 7129 FIRS 2
Johnstone, D.; Fich, M.; McCoey, C.; van Kempen, T. A.; Fuente, A.; Kristensen, L. E.; Cernicharo, J.; and 54 co-authors
Astronomy and Astrophysics
521; L41; 10/2010
4.179
Herschel/HIFI observations of water from the intermediate mass protostar NGC 7129 FIRS 2 provide a powerful diagnostic of the physical conditions in this star formation environment. Six spectral settings, covering four H216O and two H218O lines, were observed and all but one H218O line were detected. The narrower components are consistent with emission from water arising in the envelope around the intermediate mass protostar, and the abundance of H2O is constrained to ?10-7 for the outer envelope. Additionally, the presence of a narrow self-absorption component for the lowest energy lines is likely due to self-absorption from colder water in the outer envelope.


[20] Nitrogen hydrides in interstellar gas. Herschel/HIFI observations towards G10.6-0.4 (W31C)
Persson, C. M.; Black, J. H.; Cernicharo, J.; Goicoechea, J. R.; and 48 co-authors
Astronomy and Astrophysics
521; L45; 10/2010
4.179
The HIFI instrument on board the Herschel Space Observatory has been used to observe interstellar nitrogen hydrides along the sight-line towards G10.6-0.4 in order to improve our understanding of the interstellar chemistry of nitrogen. We report observations of absorption in NH N = 1 0 J = 2 1 and ortho-NH2 11,1 00,0. We also observed ortho-NH3 10 00, and 20 10, para-NH3 21 11, and searched unsuccessfully for NH+. The similar profiles suggest fairly uniform abundances relative to hydrogen, approximately 6 × 10-9, 3 × 10-9, and 3 × 10-9 for NH, NH2, and NH3, respectively. These abundances are discussed with reference to models of gas-phase and surface chemistry.


[21] Molecular content of the circumstellar disk in AB Aurigae First detection of SO in a circumstellar disk
Fuente, A.; Cernicharo, J.; Agúndez, M.; Berné, O.; Goicoechea, J. R.; Alonso-Albi, T.; Marcelino, N.
Astronomy and Astrophysics
524; A19; 12/2010
4.179
Very few molecular species have been detected in circumstellar disks surrounding young stellar objects. We are carrying out an observational study of the chemistry of circumstellar disks surrounding T Tauri and Herbig Ae stars. We detected lines of the molecules HCO+, CN, H2CO, SO, CS, and HCN toward AB Aur. In addition, we tentatively detected DCO+ and H2S lines. The line profiles suggest that the CN, HCN, H2CO, CS, and SO lines arise in the disk. This makes it the first detection of SO in a circumstellar disk. Our results demonstrate that the disk associated with AB Aur is rich in molecular species. Our chemical model shows that the detection of SO is consistent with that expected from a very young disk where the molecular adsorption onto grains does not yet dominate the chemistry.

[22] The Foggy Disks Surrounding AeBe Stars: A Theoretical Study of The HDO Lines
Ceccarelli, C.; Cernicharo, J.; Ménard, F.; Pinte, C.
The Astrophysical Journal
725; L135; 12/2010
7.436
Water is an important species that has a large influence on the chemical and physical structure of protoplanetary disks. Unfortunately, its main isotope is difficult to observe from the ground because of Earth atmosphere, with the exception of a few maser lines. A viable alternative is offered by its isotopologue HDO, for which several lines are observable (and observed) with ground telescopes. In addition, observations of the HDO lines permit us to estimate the HDO/H2O ratio, which can be a powerful diagnostic of the past history of the disk. In this Letter, we present a theoretical study of the HDO lines. We show that a few HDO lines are bright enough to be observable with ground-based telescopes.

[23] Identification of KCN in IRC+10216: Evidence for Selective Cyanide Chemistry
Pulliam, R. L.; Savage, C.; Agúndez, M.; Cernicharo, J.; Guélin, M.; Ziurys, L. M.
The Astrophysical Journal
725; L181; 12/2010
7.436
A new interstellar molecule, KCN, has been identified toward the circumstellar envelope of the carbon-rich asymptotic giant branch star, IRC+10216—the fifth metal cyanide species to be detected in space. Fourteen rotational transitions of this T-shaped, asymmetric top were searched for in the frequency range of 83-250 GHz using the Arizona Radio Observatory (ARO) 12 m Kitt Peak antenna, the IRAM 30 m telescope, and the ARO Submillimeter Telescope. Distinct lines were measured for 10 of these transitions. The presence of KCN in IRC+10216, along with MgNC, MgCN, NaCN, and AlNC, suggests that cyanide/isocyanide species are the most common metal-containing molecules in carbon-rich circumstellar gas.

[24] A molecular survey of outflow gas: velocity-dependent shock chemistry and the peculiar composition of the EHV gas
Tafalla, M.; Santiago-García, J.; Hacar, A.; Bachiller, R.
Astronomy and Astrophysics
522; A91; 11/2010
4.179
Bipolar outflows from Class 0 protostars often present two components in their CO spectra that have different kinematic behaviors: a smooth outflow wing and a discrete, extremely high-velocity (EHV) peak. We carried out a molecular survey of the outflows powered by L1448-mm and IRAS 04166+2706, two sources with prominent wing and EHV components. The different chemical compositions of the wing and EHV regimes suggest that these two outflow components have different physical origins. The wing component is better explained by shocked ambient gas, although none of the existing shock models explains all observed features. We hypothesize that the peculiar composition of the EHV gas reflects its origin as a dense wind from the protostar or its surrounding disk

[25] Molecular gas chemistry in AGN. II. High-resolution imaging of SiO emission in NGC 1068: shocks or XDR?
García-Burillo, S.; Usero, A.; Fuente, A.; and 7 co-authors
Astronomy and Astrophysics
519; A2; 09/2010
4.179
The extreme properties of molecular gas in the circum-nuclear molecular disk of NGC 1068 result from the interplay between different processes directly linked to nuclear activity. The results presented here highlight in particular the footprint of shocks and X-ray irradiation on the properties of molecular gas in this Seyfert. Whereas XDR chemistry offers a simple explanation for CN and SiO in NGC 1068, the relevance of shocks deserves further scrutiny. The inclusion of dust grain chemistry would help solve the controversy regarding the abundances of other molecular species, like HCN, which are under-predicted by XDR models

[26] Chemical study of intermediate-mass (IM) Class 0 protostars. CO depletion and N2H+ deuteration
Alonso-Albi, T.; Fuente, A.; Crimier, N.; Caselli, P.; Ceccarelli, C.; Johnstone, D.; Planesas, P.; and 6 co-authors
Astronomy and Astrophysics
518; A52; 07/2010
4.179
We are carrying out a physical and chemical study of the protostellar envelopes in a representative sample of IM Class 0 protostars. In our first paper we determined the physical structure (density-temperature radial profiles) of the protostellar envelopes. Here, we study the CO depletion and N2H+ deuteration. The deuterium fractionation is not fitted by chemical models. This discrepancy is very likely caused by the simplicity of our model that assumes spherical geometry and neglects important phenomena like the effect of bipolar outflows and UV radiation from the star. More important, the deuterium fractionation is dependent on the ortho-to-para H2 ratio, which is not likely to reach the steady-state value in the dynamical time scales of these protostars

[27] On the Sensitivity of Partial Redistribution Scattering Polarization Profiles to Various Atmospheric Parameters
Sampoorna, M.; Trujillo Bueno, J.; Landi Degl Innocenti, E.
The Astrophysical Journal
722; 1269-1289; 10/2010
7.436
This paper presents a detailed study of the scattering polarization profiles formed under partial frequency redistribution (PRD) in two thermal models of the solar atmosphere. Particular attention is given to understanding the influence of several atmospheric parameters on t
he emergent fractional linear polarization profiles. We show that complete frequency redistribution is a good approximation to model weak resonance lines. We also show that the emergent linear polarization profiles can be very sensitive to the thermal structure of the solar atmosphere and, in particular, to spatial variations of the damping parameter.

[28] A new accurate and full dimensional potential energy surface of H5+ based on a triatomics-in-molecules analytic function
Aguado, A.; Barragán, P.; Prosmiti, R.; Delgado-Barrio, G.; Villarreal, P.; Roncero, O.
Journal of Chemical Physics
133; 024306-024306-15; 07/2010
2.920
In this work a reliable full nine-dimensional potential energy surface for studying the dynamics of H5+ is constructed, which is completely symmetric under any permutation of the nuclei. For this purpose, we develop a triatoms-in-molecules method as an extension of the more common diatoms-in-molecules one, which allows a very accurate description of the asymptotic regions by including correctly the charge-induced dipole and quadrupole interactions. The global potential energy surface thus obtained in this work has an overall root mean square error of 0.079 kcal/mol for energies below 27 kcal/mol above the global well. The features of the potential are described and compared with previous available surfaces

[29] Toward a realistic density functional theory potential energy surface for the H5+ cluster
Barragán, P.; Prosmiti, R.; Roncero, O.; Aguado, A.; Villarreal, P.; Delgado-Barrio, G.
Journal of Chemical Physics
133; 054303-054303-10; 08/2010
2.920
The potential energy surface of H5+ is characterized using density functional theory. The hypersurface is evaluated at selected configurations employing different functionals, and compared with results obtained from ab initio CCSD(T) calculations. The calculated binding energy and dissociation enthalpies compare very well with previous benchmark coupled-cluster ab initio data, and with experimental data available. Based on these results the use of such approach to perform first-principles molecular dynamics simulations could provide reliable information regarding the dynamics of protonated hydrogen clusters.

[30] Reaction dynamics of the D+ + H2 system. A comparison of theoretical approaches
Jambrina, P. G.; Alvariño, J. M.; Aoiz, F. J.; Herrero, Víctor J.; Sáez-Rábanos, V.
Physical Chemistry Chemical Physics
12, 12591-12603, 2010
3.453
The dynamics of the deuteron–proton exchange D+ + H2 → HD + H+ reaction on its ground 11A′ potential energy surface has been the subject of a theoretical study for collision energies below 1.5 eV. The results obtained with three theoretical approaches: quasi-classical trajectory (QCT), statistical quasi-classical trajectory (SQCT), and accurate time-independent quantum mechanical (QM) calculations are compared in the range of collision energies from 5 meV to 0.2 eV. The deviations from the statistical behaviour of the QCT data at higher energies are remarkable. Nevertheless, on the whole, the title reaction can be deemed more statistical than the H+ + D2 reaction

[31] Ammonium and Formate Ions in Interstellar Ice Analogs
Gálvez, O.; Maté, B.; Herrero, V. J.; Escribano, R.
The Astrophysical Journal
724; 539-545; 11/2010
7.436
The so-called hyperquenching technique has been applied to generate water ices containing ammonium and formate ions by sudden freezing of droplets of NH4Cl, NH4COOH, and NaCOOH solutions. Salt deposits were obtained after heating the ices to 210 K to sublimate all water content. All stages are controlled by IR transmission spectroscopy. The NH4+ bands are very much broadened and smeared in the frozen droplets, but stand out strongly when water is eliminated. This fact hints toward the difficulty in ascertaining the presence of this species in astrophysical water-containing ices

[32] Plasma diagnostics and device properties of AlGaN/GaN HEMT passivated with SiN deposited by plasma-enhanced chemical vapour deposition
Romero, M. F.; Sanz, M. M.; Tanarro, I.; Jiménez, A.; Muñoz, E
Journal of Physics D
43; 495202; 12/2010
2.105
In this work, silicon nitride thin films have been deposited by plasma enhanced chemical vapour deposition on both silicon samples and AlGaN/GaN high electron mobility transistors (HEMT) grown on sapphire substrates. Commercial parallel-plate RF plasma equipment has been used. During depositions, the dissociation rates of SiH4 and NH3 precursors and the formation of H2 and N2 have been analysed by mass spectrometry as a function of the NH3/SiH4 flow ratio and the RF power applied to the plasma reactor. Afterwards, the properties of the films and the HEMT electrical characteristics have been studied.

[33] Instantaneous normal modes, resonances, and decay channels in the vibrational relaxation of the amide I mode of N-methylacetamide-D in liquid deuterated water
Bastida, A.; Soler, M. A.; Zúñiga, J.; Requena, A.; Kalstein, A.; Fernández-Alberti, S.
Journal of Chemical Physics
132; 224501-224501-13; 06/2010
2.920
A nonequilibrium molecular dynamics (MD) study of the vibrational relaxation of the amide I mode of deuterated N-methylacetamide (NMAD) in aqueous (D2O) solution is carried out using instantaneous normal modes (INMs). The identification of the INMs as they evolve over time, which is necessary to analyze the energy fluxes, is made by using a novel algorithm which allows us to assign unequivocally each INM to an individual equilibrium normal mode (ENM) or to a group of ENMs during the MD simulations.

[34] Molecular dynamics simulations and instantaneous normal-mode analysis of the vibrational relaxation of the C-H stretching modes of N-methylacetamide-d in liquid deuterated water
Bastida A.; Soler M.A.; Zúñiga J.; Requena A.; Kalstein A.; Fernández-Alberti S.
The Journal of Physical Chemistry A
114; 11450-61; 11/2010
2.732
Nonequilibrium molecular dynamics (MD) simulations and instantaneous normal mode (INMs) analyses are used to study the vibrational relaxation of the C-H stretching modes (ν(s)(CH₃)) of deuterated N-methylacetamide (NMAD) in aqueous (D2O) solution. All the specific relaxation channels participating in the whole relaxation process are properly identified. The results from the simulations are finally compared with the recent experimental measurements of the ?(s)(CH?) vibrational energy relaxation in NMAD/D?O(l) reported by Dlott et al. (J. Phys. Chem. A 2009, 113, 75.) using ultrafast infrared-Raman spectroscopy.

[35] Conformations of γ-Aminobutyric Acid (GABA): The Role of the n→π* Interaction
Blanco, S.; López, J. C.; Mata, S.; Alonso, J. L.
Angewandte Chemie International Edition
49; 9187–9192; 11/2010
12.730
γ-Aminobutyric acid (GABA) is arguably the most important inhibitory neurotransmitter in the brain and brainstem/spinal cord. Identifying the stable conformers of GABA can be relevant to understanding the selectivity of the biological processes in which the neurotransmitter participates. In the present work we have observed and characterized nine conformers of GABA using Fourier transform microwave spectroscopy in supersonic jets combined with laser ablation

[36] Tautomerism and Microsolvation in 2-Hydroxypyridine/2-Pyridone
Mata, S.; Cortijo, V.; Caminati, W.; Alonso, J. L.; Sanz, M. E.; López, J. C.; Blanco, S.
The Journal of Physical Chemistry A
114; 11393–11398; 11/2010
2.732
In this work we have investigated the hydrated complexes of the tautomers 2HP and
2PO with one and two water molecules by molecular beam Fourier transform microwave (MB-FTMW) spectroscopy in an attempt to prove experimentally whether there is a displacement of the 2HP/2PO equilibrium induced by water. We have observed the isolated monomers, their 1:1 water complexes, and the 2PO−(H2O)2 complex in their ground vibrational states. Careful measurements of the relative intensities of the rotational transitions have allowed us to estimate the abundance of these species in the molecular beam and determine that the tautomeric preferences of the 2HP/2PO pair change upon complexation.

[37] One- and Two-Step Ultraviolet and Infrared Laser Desorption Ionization Mass Spectrometry of Asphaltenes
Hurtado, P.; Gámez, F.; Martínez-Haya, B.
Energy & Fuels
24; 6067–6073; 10/2010
2.444
The determination of reliable molecular-weight distributions of complex asphaltene fractions has challenged modern mass spectrometry. This investigation extends previous studies on the application in this field of one-step laser desorption/ionization (LDI) and two-step laser desorption/post-ionization (L2MS) techniques employing ultraviolet (UV) and mid-infrared (IR) wavelengths. The study confirms that one-step UV−LDI easily induces aggregation of the asphaltenes. In contrast, in one-step IR−LDI and two-step UV/UV−L2MS and IR/UV−L2MS, aggregation is largely suppressed and the measurements reproduce correctly the known molecular-weight distribution of the model asphaltenes, with a bulk of constituents within m/z 200−1000.

[38] Nanoparticle TiO2 Films Prepared by Pulsed Laser Deposition: Laser Desorption and Cationization of Model Adsorbates
Gámez, F.; Plaza-Reyes, A.; Hurtado, P.; Guillén, E.; Anta, J. E.; Martínez-Haya, B; and 5 co-authors
The Journal of Physical Chemistry C
114; 17409–17415; 10/2010
4.520
Titanium dioxide is a low-cost photocatalytic material in the chemical industry. This work provides extended insights into the use of TiO2 nanostructures in laser-assisted laser desorption ionization (LDI) of small peptides and synthetic polymers. The best LDI performance is found for nanosecond PLD crystalline substrates of the anatase polymorph and for femtosecond PLD amorphous substrates, with average nanoparticle sizes in both cases in the range of 25−55 nm

[39] Quantum mechanical mechanisms of inelastic and reactive H + D2(v = 0, j = 2) collisions
Aldegunde, J.; Jambrina, P. G.; Sáez-Rábanos, V.; de Miranda, M. P.; Aoiz, F. J.
Physical Chemistry Chemical Physics
12; 13626-13636; 09/2010
3.453
This article analyses the mechanisms of inelastic and reactive H + D2(v = 0, j = 2) collisions that result in highly vibrationally excited products when the collision energy is 1.70 eV. The analytical method is entirely quantum mechanical and focuses on correlations between the polarization of the reactant molecule and the direction of product scattering. The results presented in this article complement, extend and throw some new light on recent advances in the understanding of the most studied of elementary chemical reactions.

[40] Nonequilibrium processes in supersonic jets of N2, H2, and N2 + H2 mixtures: (II) shock waves
Ramos, A.; Tejeda, G.; Fernández, J. M.; Montero, S.
The Journal of Physical Chemistry A
114; 7761-8; 08/2010
2.732
We report an experimental study of the shock wave system of three continuous axisymmetric jets of pure N(2) and H(2), and of the N(2) + 2H(2) mixture, generated at p(0) = 1 bar and T(0) = 295 K through a D = 310 microm cylindrical nozzle against a background pressure p(b) = 6.1 mbar. Number density and rotational populations have been measured by Raman spectroscopy with high spatial resolution (approximately 15 microm). In the N(2) + 2H(2) mixture the different behavior of the two species leads to a localized enrichment of the light component up to 20%, which might provide the basis for an efficient separation device.

[41] HIFI spectroscopy of low-level water transitions in M 82
Weiß, A.; Requena-Torres, M. A.; Güsten, R.; García-Burillo, S.; and 22 co-authors
Astronomy and Astrophysics
521; L1; 10/2010
4.179
We present observations of the rotational ortho-water ground transition, the two lowest para-water transitions, and the ground transition of ionised ortho-water in the archetypal starburst galaxy M 82, performed with the HIFI instrument on the Herschel Space Observatory. These observations are the first detections of the para-H2O(111-000) (1113 GHz) and ortho-H2O+(111-000) (1115 GHz) lines in an extragalactic source. This indicates that water is not associated with small, dense cores within the ISM of M 82 but arises from a more widespread diffuse gas component.