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Cabezas C, Kawashima Y, Bermúdez C, Usami T, Hirota E, Cernicharo J. The conformational behavior of N‑ethylformamide as observed by rotational spectroscopy and quantum chemistry. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2023; 291:122353. [PMID: 36646042 DOI: 10.1016/j.saa.2023.122353] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Revised: 12/15/2022] [Accepted: 01/08/2023] [Indexed: 06/17/2023]
Abstract
A peptide linkage (CO)NH containing molecule, N-ethylformamide, was investigated by rotational spectroscopy in order to determine the molecular constants of its highest-energy conformer, cis-ac. Its rotational spectrum was observed in two different frequency ranges, in the 4-26 GHz frequency region using a Fourier transform microwave spectrometer and at millimeter wave frequencies between 75 and 116 GHz, employing a broadband high-resolution rotational spectrometer. The measurements at low frequencies allowed to resolve the hyperfine structure components due to nitrogen nuclear quadrupole coupling while the data at higher frequencies provided spectroscopic information about high order centrifugal effects. From a merged fit using all the observational data we have determined a total of thirteen molecular constants that provide a more accurate spectral modelling of the cis-ac conformer and serves a basis for their astronomical search. We have also observed spectra of five singly substituted isotopologues for the cis-ac conformer, three 13C and one for each of 15N and the deuterated species on the N-D position, from which we derived a partial r0 structure, in fair agreement with an ab initio result. In addition, the rotational transitions of the deuterated species of the most stable trans-sc conformer were observed and assigned and three rotational, five centrifugal distortion constants and nuclear quadrupole coupling constants of the nitrogen and deuterium nuclei were determined.
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Affiliation(s)
- Carlos Cabezas
- Instituto de Física Fundamental (IFF-CSIC), Group of Molecular Astrophysics, C/ Serrano 121, Madrid 28006, Spain.
| | - Yoshiyuki Kawashima
- Department of Applied Chemistry, Faculty of Engineering, Kanagawa Institute of Technology, Atsugi, Kanagawa 243-0292, Japan.
| | - Celina Bermúdez
- Departamento de Química Física y Química Inorgánica, Facultad de Ciencias-I.U. CINQUIMA, Universidad de Valladolid, Paseo de Belén 7, Valladolid 47011, Spain
| | - Tsuyoshi Usami
- Department of Applied Chemistry, Faculty of Engineering, Kanagawa Institute of Technology, Atsugi, Kanagawa 243-0292, Japan
| | - Eizi Hirota
- The Graduate University for Advanced Studies, Hayama, Kanagawa 243-0193, Japan
| | - José Cernicharo
- Instituto de Física Fundamental (IFF-CSIC), Group of Molecular Astrophysics, C/ Serrano 121, Madrid 28006, Spain
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Hermanns M, Wehres N, Heyne B, Honingh CE, Graf UU, Schlemmer S. Performance of a chirped-pulse Fourier transform millimeter wave spectrometer in the range of 75-110 GHz. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2023; 94:034705. [PMID: 37012769 DOI: 10.1063/5.0141579] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Accepted: 02/21/2023] [Indexed: 06/19/2023]
Abstract
We present a home-built chirped-pulse Fourier transform millimeter wave (CP-FTMMW) spectrometer. The setup is devoted to the sensitive recording of high-resolution molecular spectroscopy in the W band between 75 and 110 GHz. We describe the experimental setup in detail, including a characterization of the chirp excitation source, the optical beam path, and the receiver. The receiver is a further development of our 100 GHz emission spectrometer. The spectrometer is equipped with a pulsed jet expansion and a DC discharge. Spectra of methyl cyanide as well as hydrogen cyanide (HCN) and hydrogen isocyanide (HNC) products from the DC discharge of this molecule are recorded to characterize the performance of the CP-FTMMW instrument. The formation of the HCN isomer is favored by a factor of 63 with respect to HNC. Hot/cold calibration measurements enable a direct comparison of the signal and noise levels of the CP-FTMMW spectra to those of the emission spectrometer. For the CP-FTMMW instrument, we find many orders of magnitude of signal enhancement and a much stronger noise reduction due to the coherent detection scheme.
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Affiliation(s)
- M Hermanns
- I. Physikalisches Institut, Zülpicher Str. 77, 50937 Köln, Germany
| | - N Wehres
- I. Physikalisches Institut, Zülpicher Str. 77, 50937 Köln, Germany
| | - B Heyne
- I. Physikalisches Institut, Zülpicher Str. 77, 50937 Köln, Germany
| | - C E Honingh
- I. Physikalisches Institut, Zülpicher Str. 77, 50937 Köln, Germany
| | - U U Graf
- I. Physikalisches Institut, Zülpicher Str. 77, 50937 Köln, Germany
| | - S Schlemmer
- I. Physikalisches Institut, Zülpicher Str. 77, 50937 Köln, Germany
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Cabezas C, Neeman EM, Tercero B, Bermúdez C, Cernicharo J. Comprehensive rotational study and astronomical search for cyclopropanecarboxaldehyde. ASTRONOMY AND ASTROPHYSICS 2021; 645:A75. [PMID: 33833467 PMCID: PMC7610548 DOI: 10.1051/0004-6361/202039924] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
CONTEXT At least a dozen molecules with a formyl group (HCO) have been observed to date in the interstellar medium (ISM), suggesting that other such species exist and remain to be discovered. However, there is still a lack of high-resolution spectroscopic data for simple molecular species of this type that could provide a basis for their detection. AIMS Cyclopropanecarboxaldehyde, c-C3H5CHO, is a small molecule containing a formyl group and is therefore an interesting candidate for astrophysical detection. The rotational spectrum of cyclopropanecarboxaldehyde has been observed before, but its experimental rotational parameters are not precise enough to allow its detection in the millimetre-wave domain. METHODS We measured the rotational spectrum of cyclopropanecarboxaldehyde in the frequency ranges 31.5-50 GHz and 72-116.5 GHz using the GACELA (GAS CEll for Laboratory Astrophysics) broadband high-resolution rotational spectrometer constructed at the Yebes Observatory. The spectroscopic study was supported by high-level theoretical calculations which were used in the identification of the vibrational excited states of cyclopropanecarboxaldehyde. RESULTS Our analysis of the rotational spectrum of cyclopropanecarboxaldehyde allowed us to obtain accurate rotational parameters for the ground state of both cis and trans isomers, which were used to derive sufficiently reliable predictions up to 300 GHz. In addition to the ground states, we identified 12 and 6 vibrationally excited states for the trans and cis isomers, respectively, including fundamental modes, multiple excitation quanta, and combination states. We find that the gas phase concentration of the trans isomer is almost 1.2 times larger than that of the cis one. These new experimental rotational parameters were employed to search for cyclopropanecarboxaldehyde in the warm molecular clouds Orion KL and Sgr B2(N) using the spectral surveys captured by ALMA (Orion) and IRAM 30 m (Sgr) at 1 mm and 3 mm, respectively.
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Affiliation(s)
- C. Cabezas
- Instituto de Física Fundamental (IFF-CSIC). Group of Molecular Astrophysics, C/Serrano 123, 28006 Madrid, Spain
| | - E. M. Neeman
- Departamento de Química Física. Facultad de Ciencias y Tecnologías Químicas. Universidad de Castilla-La Mancha. Avda. Camilo José Cela 1B. 13071, Ciudad Real, Spain
| | - B. Tercero
- Observatorio de Yebes (IGN), Cerro de la Palera s/n, 19141 Yebes, Guadalajara, Spain
- Observatorio Astronómico Nacional (OAN-IGN), C/Alfonso XII 3, 28014 Madrid, Spain
| | - C. Bermúdez
- Instituto de Física Fundamental (IFF-CSIC). Group of Molecular Astrophysics, C/Serrano 123, 28006 Madrid, Spain
| | - J. Cernicharo
- Instituto de Física Fundamental (IFF-CSIC). Group of Molecular Astrophysics, C/Serrano 123, 28006 Madrid, Spain
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Santoro G, Sobrado JM, Tajuelo-Castilla G, Accolla M, Martínez L, Azpeitia J, Lauwaet K, Cernicharo J, Ellis GJ, Martín-Gago JÁ. INFRA-ICE: An ultra-high vacuum experimental station for laboratory astrochemistry. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2020; 91:124101. [PMID: 33379937 PMCID: PMC7116743 DOI: 10.1063/5.0027920] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2020] [Accepted: 11/16/2020] [Indexed: 06/12/2023]
Abstract
Laboratory astrochemistry aims at simulating, in the laboratory, some of the chemical and physical processes that operate in different regions of the universe. Amongst the diverse astrochemical problems that can be addressed in the laboratory, the evolution of cosmic dust grains in different regions of the interstellar medium (ISM) and its role in the formation of new chemical species through catalytic processes present significant interest. In particular, the dark clouds of the ISM dust grains are coated by icy mantles and it is thought that the ice-dust interaction plays a crucial role in the development of the chemical complexity observed in space. Here, we present a new ultra-high vacuum experimental station devoted to simulating the complex conditions of the coldest regions of the ISM. The INFRA-ICE machine can be operated as a standing alone setup or incorporated in a larger experimental station called Stardust, which is dedicated to simulate the formation of cosmic dust in evolved stars. As such, INFRA-ICE expands the capabilities of Stardust allowing the simulation of the complete journey of cosmic dust in space, from its formation in asymptotic giant branch stars to its processing and interaction with icy mantles in molecular clouds. To demonstrate some of the capabilities of INFRA-ICE, we present selected results on the ultraviolet photochemistry of undecane (C11H24) at 14 K. Aliphatics are part of the carbonaceous cosmic dust, and recently, aliphatics and short n-alkanes have been detected in situ in the comet 67P/Churyumov-Gerasimenko.
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Affiliation(s)
- Gonzalo Santoro
- Instituto de Ciencia de Materiales de Madrid (ICMM, CSIC). Materials Science Factory. Structure of Nanoscopic Systems Group. c/ Sor Juana Ines de la Cruz 3, E-28049 Cantoblanco, Madrid, Spain
| | - Jesús. M. Sobrado
- Centro de Astrobiología (CAB, INTA-CSIC). Crta. de Torrejón a Ajalvir km4, E-28850, Torrejón de Ardoz, Madrid, Spain
| | - Guillermo Tajuelo-Castilla
- Instituto de Ciencia de Materiales de Madrid (ICMM, CSIC). Materials Science Factory. Structure of Nanoscopic Systems Group. c/ Sor Juana Ines de la Cruz 3, E-28049 Cantoblanco, Madrid, Spain
| | - Mario Accolla
- Instituto de Ciencia de Materiales de Madrid (ICMM, CSIC). Materials Science Factory. Structure of Nanoscopic Systems Group. c/ Sor Juana Ines de la Cruz 3, E-28049 Cantoblanco, Madrid, Spain
| | - Lidia Martínez
- Instituto de Ciencia de Materiales de Madrid (ICMM, CSIC). Materials Science Factory. Structure of Nanoscopic Systems Group. c/ Sor Juana Ines de la Cruz 3, E-28049 Cantoblanco, Madrid, Spain
| | - Jon Azpeitia
- Instituto de Ciencia de Materiales de Madrid (ICMM, CSIC). Materials Science Factory. Structure of Nanoscopic Systems Group. c/ Sor Juana Ines de la Cruz 3, E-28049 Cantoblanco, Madrid, Spain
| | - Koen Lauwaet
- IMDEA Nanociencia. Ciudad Universitaria de Cantoblanco, E-28049 Cantoblanco, Madrid, Spain
| | - José Cernicharo
- Instituto de Física Fundamental (IFF, CSIC). Group of Molecular Astrophysics. c/ Serrano 123, 28006 Madrid, Spain
| | - Gary J. Ellis
- Instituto de Ciencia y Tecnología de Polímeros (ICTP, CSIC). c/ Juan de la Cierva 3, E-28006 Madrid, Spain
| | - José Ángel Martín-Gago
- Instituto de Ciencia de Materiales de Madrid (ICMM, CSIC). Materials Science Factory. Structure of Nanoscopic Systems Group. c/ Sor Juana Ines de la Cruz 3, E-28049 Cantoblanco, Madrid, Spain
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Cabezas C, Bermúdez C, Gallego JD, Tercero B, Hernández JM, Tanarro I, Herrero VJ, Doménech JL, Cernicharo J. The millimeter-wave spectrum and astronomical search of succinonitrile and its vibrational excited states ★. ASTRONOMY AND ASTROPHYSICS 2019; 629:A35. [PMID: 31485081 PMCID: PMC6726483 DOI: 10.1051/0004-6361/201935899] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
CONTEXT Dinitriles with a saturated hydrocarbon skeleton and a -C≡N group at each end can have large electric dipole moments. Their formation can be related to highly reactive radicals such as CH2CN, C2N or CN. Thus, these saturated dinitriles are potential candidates to be observed in the ISM. AIMS Our goal is the investigation of the rotational spectrum of one of the simplest dinitriles N≡C-CH2-CH2-C≡N, succinonitrile, whose actual rotational parameters are not precise enough to allow its detection in the ISM. In addition, the rotational spectra for its vibrational exicted states will be analyzed. METHODS The rotational spectra of succinonitrile was measured in the frequency range 72-116.5 GHz using a new broadband millimeter-wave spectrometer based on radio astronomy receivers with Fast Fourier Transform backends. The identification of the vibrational excited states of succinonitrile was supported by high-level ab initio calculations on the harmonic and anharmonic force fields. RESULTS A total of 459 rotational transitions with maximum values of J and Ka quantum numbers 70 and 14, respectively, were measured for the ground vibrational state of succinonitrile. The analysis allowed us to accurately determine the rotational, quartic and sextic centrifugal distortion constants. Up to eleven vibrational excited states, resulting from the four lowest frequency vibrational modes ν 13, ν 12, ν 24 and ν 23 were identified. In addition to the four fundamental modes, we observed overtones together with some combination states. The rotational parameters for the ground state were employed to unsuccessfully search for succinonitrile in the cold and warm molecular clouds Orion KL, Sgr B2(N), B1-b and TMC-1, using the spectral surveys captured by IRAM 30m at 3mm and the Yebes 40m at 1.3cm and 7mm. CONCLUSIONS
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Affiliation(s)
- C. Cabezas
- Instituto de Física Fundamental (IFF-CSIC). Group of Molecular Astrophysics, C/ Serrano 123, 28006 Madrid, Spain
| | - C. Bermúdez
- Instituto de Física Fundamental (IFF-CSIC). Group of Molecular Astrophysics, C/ Serrano 123, 28006 Madrid, Spain
| | - J. D. Gallego
- Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
| | - B. Tercero
- Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
- Observatorio Astronómico Nacional (OAN-IGN), C/ Alfonso XII 3, 28014 Madrid, Spain
| | - J. M. Hernández
- Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
| | - I. Tanarro
- Instituto de Estructura de la Materia (IEM-CSIC). Molecular Physics Department. C/Serrano 123, 28006 Madrid, Spain
| | - V. J. Herrero
- Instituto de Estructura de la Materia (IEM-CSIC). Molecular Physics Department. C/Serrano 123, 28006 Madrid, Spain
| | - J. L. Doménech
- Instituto de Estructura de la Materia (IEM-CSIC). Molecular Physics Department. C/Serrano 123, 28006 Madrid, Spain
| | - J. Cernicharo
- Instituto de Física Fundamental (IFF-CSIC). Group of Molecular Astrophysics, C/ Serrano 123, 28006 Madrid, Spain
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Cernicharo J, Gallego JD, López-Pérez JA, Tercero F, Tanarro I, Beltrán F, de Vicente P, Lauwaet K, Alemán B, Moreno E, Herrero VJ, Doménech JL, Ramírez SI, Bermúdez C, Peláez RJ, Patino-Esteban M, López-Fernández I, García-Álvaro S, García-Carreño P, Cabezas C, Malo I, Amils R, Sobrado J, Diez-González C, Hernandéz J, Tercero B, Santoro G, Martínez L, Castellanos M, Vaquero Jiménez B, Pardo JR, Barbas L, López-Fernández J, Aja B, Leuther A, Martín-Gago JA. Broad band high resolution rotational spectroscopy for Laboratory Astrophysics. ASTRONOMY AND ASTROPHYSICS 2019; 626:10.1051/0004-6361/201935197. [PMID: 31186577 PMCID: PMC6557716 DOI: 10.1051/0004-6361/201935197] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We present a new experimental setup devoted to the study of gas phase molecules and processes using broad band high spectral resolution rotational spectroscopy. A reactor chamber has been equipped with radio receivers similar to those used by radio astronomers to search for molecular emission in space. The whole Q (31.5-50 GHz) and W bands (72-116.5 GHz) are available for rotational spectroscopy observations. The receivers are equipped with 16×2.5 GHz Fast Fourier Transform spectrometers with a spectral resolution of 38.14 kHz allowing the simultaneous observation of the complete Q band and one third of the W band. The whole W band can be observed in three settings in which the Q band is always observed. Species such as CH3CN, OCS, and SO2 are detected, together with many of their isotopologues and vibrationally excited states, in very short observing times. The system permits automatic overnight observations and integration times as long as 2.4×105 seconds have been reached. The chamber is equipped with a radiofrequency source to produce cold plasmas and with four ultraviolet lamps to study photochemical processes. Plasmas of CH4, N2, CH3CN, NH3, O2, and H2, among other species, have been generated and the molecular products easily identified by their rotational spectrum, and mass spectrometry and optical spectroscopy. Finally, the rotational spectrum of the lowest energy conformer of CH3CH2NHCHO (N-Ethylformamide), a molecule previously characterized in microwave rotational spectroscopy, has been measured up to 116.5 GHz allowing the accurate determination of its rotational and distortion constants and its search in space.
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Affiliation(s)
- J. Cernicharo
- Instituto de Física Fundamental (IFF. CSIC). Group of Molecular Astrophysics, C/Serrano 123, 28006 Madrid, Spain
| | - J. D. Gallego
- Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
| | - J. A. López-Pérez
- Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
| | - F. Tercero
- Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
| | - I. Tanarro
- Instituto de Estructura de la Materia (IEM. CSIC). Molecular Physics Department. C/Serrano 123, 28006 Madrid, Spain
| | - F. Beltrán
- Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
| | - P. de Vicente
- Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
| | - K. Lauwaet
- Instituto de Ciencia de Materiales de Madrid (ICMM. CSIC). Materials Science Factory. Structure of Nanoscopic Systems Group, ESISNA. C/Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Madrid, Spain
- IMDEA Nanociencia, Ciudad Universitaria de Cantoblanco, 28049 Cantoblanco, Madrid, Spain
| | - B. Alemán
- Instituto de Ciencia de Materiales de Madrid (ICMM. CSIC). Materials Science Factory. Structure of Nanoscopic Systems Group, ESISNA. C/Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Madrid, Spain
- IMDEA Materiales, C/Eric Kandel 2, Tecnogetafe, 28906 Getafe, Madrid, Spain
| | - E. Moreno
- Instituto de Física Fundamental (IFF. CSIC). Group of Molecular Astrophysics, C/Serrano 123, 28006 Madrid, Spain
| | - V. J. Herrero
- Instituto de Estructura de la Materia (IEM. CSIC). Molecular Physics Department. C/Serrano 123, 28006 Madrid, Spain
| | - J. L. Doménech
- Instituto de Estructura de la Materia (IEM. CSIC). Molecular Physics Department. C/Serrano 123, 28006 Madrid, Spain
| | - S. I. Ramírez
- Instituto de Física Fundamental (IFF. CSIC). Group of Molecular Astrophysics, C/Serrano 123, 28006 Madrid, Spain
- Centro de Investigaciones Químicas, UAEM. Av. Universidad, 1001 Col. Chamilpa 62209, Cuernavaca, Morelos Mexico
| | - C. Bermúdez
- Instituto de Física Fundamental (IFF. CSIC). Group of Molecular Astrophysics, C/Serrano 123, 28006 Madrid, Spain
| | - R. J. Peláez
- Instituto de Estructura de la Materia (IEM. CSIC). Molecular Physics Department. C/Serrano 123, 28006 Madrid, Spain
| | - M. Patino-Esteban
- Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
| | - I. López-Fernández
- Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
| | - S. García-Álvaro
- Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
| | - P. García-Carreño
- Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
| | - C. Cabezas
- Instituto de Física Fundamental (IFF. CSIC). Group of Molecular Astrophysics, C/Serrano 123, 28006 Madrid, Spain
| | - I. Malo
- Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
| | - R. Amils
- Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
| | - J. Sobrado
- Centro de Astrobiología (CSIC-INTA), Crta. de Torrejón de Ardoz a Ajalvir, km 4. Torrejón de Ardoz, 28850, Spain
| | - C. Diez-González
- Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
| | - J.M. Hernandéz
- Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
| | - B. Tercero
- Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
| | - G. Santoro
- Instituto de Ciencia de Materiales de Madrid (ICMM. CSIC). Materials Science Factory. Structure of Nanoscopic Systems Group, ESISNA. C/Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Madrid, Spain
| | - L. Martínez
- Instituto de Ciencia de Materiales de Madrid (ICMM. CSIC). Materials Science Factory. Structure of Nanoscopic Systems Group, ESISNA. C/Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Madrid, Spain
| | - M. Castellanos
- Instituto de Física Fundamental (IFF. CSIC). Group of Molecular Astrophysics, C/Serrano 123, 28006 Madrid, Spain
| | - B. Vaquero Jiménez
- Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
| | - J. R. Pardo
- Instituto de Física Fundamental (IFF. CSIC). Group of Molecular Astrophysics, C/Serrano 123, 28006 Madrid, Spain
| | - L. Barbas
- Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
| | - J.A. López-Fernández
- Centro de Desarrollos Tecnológicos, Observatorio de Yebes (IGN), 19141 Yebes, Guadalajara, Spain
| | - B. Aja
- Universidad de Cantabria, Department of Communication Engineering, Avda. Los Castros, 39005 Santander, Spain
| | - A. Leuther
- Fraunhofer Institut fur Angewandte Festkorperphysik, Tullastresse 72, 79108 Freiburg, Germany
| | - J. A. Martín-Gago
- Instituto de Ciencia de Materiales de Madrid (ICMM. CSIC). Materials Science Factory. Structure of Nanoscopic Systems Group, ESISNA. C/Sor Juana Inés de la Cruz 3, 28049 Cantoblanco, Madrid, Spain
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