Magna Santos - Academia.edu (original) (raw)

Papers by Magna Santos

Research paper thumbnail of IR laser-induced process for chemical vapor deposition of polyselenocarbosilane films

Journal of Analytical and Applied Pyrolysis, 2006

TEA CO2 laser irradiation into gaseous mixtures of 1,3-disilacyclobutane (DSCB) and dimethyl sele... more TEA CO2 laser irradiation into gaseous mixtures of 1,3-disilacyclobutane (DSCB) and dimethyl selenide (DMS) results in infrared multiple photon-induced, non-interacting homogeneous decompositions of both educts, one yielding silene (H2SiCH2) and the other elemental selenium as major products. The reaction between polymerizing silene and agglomerizing Se leads to chemical vapor deposition of novel polyselenocarbosilane films which are unstable in atmosphere. The

Research paper thumbnail of IR laser-induced co-decomposition of dimethyl selenide and trisilane: Gas-phase formation of SiSe and chemical vapor deposition of nanostructured H/Si/Se/C polymers

Journal of Photochemistry and Photobiology A-chemistry, 2007

Chemical changes in IR laser irradiated gaseous mixtures of dimethyl selenide and trisilane have ... more Chemical changes in IR laser irradiated gaseous mixtures of dimethyl selenide and trisilane have been diagnosed by laser-induced fluorescence (LIF) of transient species and by FTIR, Raman, photoelectron spectroscopy and electron microscopy of the final solid products deposited from the gas phase. It is revealed that decomposition of both compounds leads to gas-phase formation of SiSe and deposition of solid nanostructured polymeric materials. We present indirect evidence on the presence of Si Se bonds in these polymers by revealing that these polymers undergo hydrolysis in air to H 2 Se and CH 3 SeH, which converts them to solid silicone-based films containing elemental selenium. Plausible reactions taking place in the gas phase and upon exposure of solids to air are suggested.

Research paper thumbnail of Infrared laser-induced chemistry of chlorodifluoromethane?silane mixtures at two irradiating wavelengths

Journal of The Chemical Society, Faraday Transactions, 1993

... irradiating line [fluence/J cm-,] energy absorbed" (YO) 9R(34) C2.61 + lOP(20) [1.4] 9P(... more ... irradiating line [fluence/J cm-,] energy absorbed" (YO) 9R(34) C2.61 + lOP(20) [1.4] 9P(34)Cl.51 + lOP(20) C1.31 lOP(20) [ 1.41 lOP(20) C1.8) + lOP(20) c1.4) 9P(34) C2.1) 20-2 1 24-26 21 3b With time delay 0-1 ps. No decomposition. wavelengths experiments. ...

Research paper thumbnail of Gas-phase formation of SiSe in IR laser-co-decomposition of dimethyl selenide and 1,3-disilacyclobutane

Journal of Organometallic Chemistry, 2007

A LIF excitation spectrum of SiSe obtained upon IR laser irradiation of gaseous mixture of 1,3-di... more A LIF excitation spectrum of SiSe obtained upon IR laser irradiation of gaseous mixture of 1,3-disilacyclobutane and dimethyl selenide reveals that the previously reported infrared multiple photon co-decomposition of both compounds involves formation of SiSe. The SiSe formation is explained in terms of reaction of Se atoms with RHSi: silylenes (R = CH 3 , H) and silene, and elimination of RH from silaneselones (RHSiSe, R = CH 3 , H).

Research paper thumbnail of IR laser-induced thermolysis of (chloromethyl)silane: complex reaction involving H2Si:, H2C: and HClSi: transients and yielding nanostructured Si/C/H phases

Journal of Materials Chemistry, 2002

Page 1. IR laser-induced thermolysis of (chloromethyl)silane: complex reaction involving H2Si:, H... more Page 1. IR laser-induced thermolysis of (chloromethyl)silane: complex reaction involving H2Si:, H2C: and HClSi: transients and yielding nanostructured Si/C/H phases Josef Pola,*a Magna Santos,b Luis Dıaz,b Kristýna Jursıková ...

Research paper thumbnail of Silicon Oxide Cluster Formation and Stability in the Laser Ablation of SiO Targets

Journal of Physical Chemistry A, 2009

The formation mechanism and stability of silicon oxide clusters observed in the ablation of SiO t... more The formation mechanism and stability of silicon oxide clusters observed in the ablation of SiO targets at 266 nm were investigated by time-of-flight mass spectrometry, laser-induced fluorescence (LIF), and DFT calculations. Neutral and positively charged Sin+/0 and SinOmH0,1+ clusters were identified in the plume, but neutral SinOm could not be observed. The time distribution of SiO in the plume measured by postionization with an ArF laser (Δλ ≈ 1 nm, τ ≈ 14 ns) and mass spectrometric detection was compared with that obtained by LIF with narrowband dye laser selective excitation of one specific rovibronic transition in SiO. Postionization leads to a multicomponent distribution that extends up to times near 100 μs after ablation, whereas LIF measurements obtain time distributions shorter than 20 μs. DFT calculations of several SinOm0/+ were performed, showing that one photon absorption of the postionization laser makes available low-energy dissociation channels of the neutrals, whereas two photon absorption is required for ionization. DFT calculations were carried out for stoichiometric H-containing clusters SinOnH+ (n = 1-4). For n = 1,2, the optimized geometries involve bonding of hydrogen to one oxygen atom in the clusters; for n = 3 and 4, the structures containing H-Si bonds are more stable.

Research paper thumbnail of IR laser-induced decomposition of 2-chloroethenylsilane for chemical vapour deposition of Si/C phases

Journal of Materials Chemistry, 1996

Infrared multiphoton decomposition of 2-chloroethenylsilane is dominated by dehydrochlorination a... more Infrared multiphoton decomposition of 2-chloroethenylsilane is dominated by dehydrochlorination and by decomposition of the intermediary ethynylsilane, and it affords a solid material consisting of an Si/C/H polymer and silicon carbide. The content of the latter ...

Research paper thumbnail of Plume investigations of the mechanisms of SiO laser ablation at 266 nm

Journal of Physics: Conference Series, 2007

The ablation mechanism of SiO at the laser wavelength of 266 nm has been investigated by characte... more The ablation mechanism of SiO at the laser wavelength of 266 nm has been investigated by characterizing the composition and dynamics of neutral and charged particles produced in the ablation. The neutral and ionized composition of the plume and the dynamics of neutral SiO were investigated by time-of-flight mass spectrometry. The velocity distribution of neutral SiO molecules shows contributions of slow and fast components. The velocity distributions of charged species in the plume were investigated by a Langmuir probe technique, obtaining that the distributions shift towards higher velocities with increasing distance from the target surface. The fastest component of the velocity distribution of neutral SiO overlaps the slowest part of the velocity distribution of charged species. The average rotational energy of SiO molecules, estimated by LIF spectroscopy does not allow to draw clear conclusions about the participation of silicon oxide ion clusters as the precursors of fast SiO molecules in the plume.

Research paper thumbnail of IR and UV laser-induced photolysis of 2-chloroethenylsilane

Journal of Photochemistry and Photobiology A-chemistry, 1997

The laser-induced decomposition of 2-chloroethenylsilane was studied in the IR with a TEA CO 2 la... more The laser-induced decomposition of 2-chloroethenylsilane was studied in the IR with a TEA CO 2 laser and in the UV with a narrow-band, frequency-doubled dye laser at 212.5 nm. Silylene was observed in the IR multiphoton dissociation (MPD) via laser-induced fluorescence ...

Research paper thumbnail of IR laser-induced chemical vapor deposition of carbon-coated iron nanoparticles embedded in polymer

Journal of Materials Chemistry, 2005

Co-decomposition of gaseous mixtures of silacyclopent-3-ene and Fe (CO) 5 by irradiation at (9+ 1... more Co-decomposition of gaseous mixtures of silacyclopent-3-ene and Fe (CO) 5 by irradiation at (9+ 10) and (9+ 10+ 5) µm from two CO 2 lasers is reported. In a one-step process, this produced nanosized (α-Fe)-based particles that consist of both superparamagnetic and ...

Research paper thumbnail of IR laser-induced co-decomposition of trisilane and thiirane for deposition of polycarbosilthiane films

Journal of Analytical and Applied Pyrolysis, 2008

ABSTRACT TEA CO2 laser irradiation of gaseous trisilane–thiirane mixtures results in the co-decom... more ABSTRACT TEA CO2 laser irradiation of gaseous trisilane–thiirane mixtures results in the co-decomposition of both components and allows chemical vapor deposition of polycarbosilthiane films that undergo reaction with air moisture, evolve H2S and develop to polycarbosiloxanes. Laser-induced fluorescence experiments allowed detection of transient SiS in the gas phase. The gas-phase formation of SiS and polycarbosilthiane, accounted for on the basis GC/MS analysis of final volatile products and in situ measured FTIR spectra of the deposited polymers, involves reactions between silylenes and S atoms that are respective intermediates of trisilane and thiirane decomposition.

Research paper thumbnail of IR laser-induced thermolysis of silacyclopent-3-ene: extrusion of silylene and chemical vapour deposition of polycarbosilane phases via reactions of silylene, buta-1,3-diene and methylene

Journal of Organometallic Chemistry, 2000

Infrared laser-induced (SF 6 ) photosensitized decomposition and infrared laser multiphoton decom... more Infrared laser-induced (SF 6 ) photosensitized decomposition and infrared laser multiphoton decomposition of silacyclopent-3ene occur as extrusion of silylene, yielding butadiene as a major gaseous product and affording chemical vapour deposition of solid saturated polycarbosilane films. The involvement of H 2 Si:, H 2 C: and buta-1,3-diene in the formation of the films is revealed through quantification of the gaseous products and identification of H 2 Si: and H 2 C: by laser induced fluorescence.

Research paper thumbnail of Silicon Oxide Cluster Formation and Stability in the Laser Ablation of SiO Targets

Journal of Physical Chemistry A, 2009

The formation mechanism and stability of silicon oxide clusters observed in the ablation of SiO t... more The formation mechanism and stability of silicon oxide clusters observed in the ablation of SiO targets at 266 nm were investigated by time-of-flight mass spectrometry, laser-induced fluorescence (LIF), and DFT calculations. Neutral and positively charged Si(n)(+/0) and Si(n)O(m)H(0,1)(+) clusters were identified in the plume, but neutral Si(n)O(m) could not be observed. The time distribution of SiO in the plume measured by postionization with an ArF laser (Delta lambda approximately 1 nm, tau approximately 14 ns) and mass spectrometric detection was compared with that obtained by LIF with narrowband dye laser selective excitation of one specific rovibronic transition in SiO. Postionization leads to a multicomponent distribution that extends up to times near 100 micros after ablation, whereas LIF measurements obtain time distributions shorter than 20 micros. DFT calculations of several Si(n)O(m)(0/+) were performed, showing that one photon absorption of the postionization laser makes available low-energy dissociation channels of the neutrals, whereas two photon absorption is required for ionization. DFT calculations were carried out for stoichiometric H-containing clusters Si(n)O(n)H(+) (n = 1-4). For n = 1,2, the optimized geometries involve bonding of hydrogen to one oxygen atom in the clusters; for n = 3 and 4, the structures containing H-Si bonds are more stable.

Research paper thumbnail of Transient detection in infrared multiphoton decomposition of (chloromethyl)silane and 1,3-disilacyclobutane: evidence for cleavage of SiCH 4 intermediates

Journal of Photochemistry and Photobiology A-chemistry, 2002

The transients produced in the infrared multiphoton decomposition (IRMPD) of (chloromethyl)silane... more The transients produced in the infrared multiphoton decomposition (IRMPD) of (chloromethyl)silane-HClSi:, H 2 Si: and H 2 C:-and of 1,3-disilacyclobutane-H 2 Si: and H 2 C:-have been identified by laser-induced fluorescence (LIF). The nascent HClSi: and H 2 Si: populations are generated with a high degree of excitation and the species produced from (chloromethyl)silane possess more rotational and vibrational energy than those produced from 1,3-disilacyclobutane. The obtained quenching rate and radiative lifetime for HClSi: are (4.6± 0.3) × 10 −10 cm 3 per molecule s −1 and 369 ± 10 ns, respectively. The formation of H 2 Si: and H 2 C: in IRMPD of both (chloromethyl)silane and 1,3-disilacyclobutane adds to previous knowledge on decomposition of (chloromethyl)silane and 1,3-disilacyclobutane and suggests that these transients are produced from the same SiCH 4 (H 3 Si(H)C: and (CH 3 )HSi:) intermediates.

Research paper thumbnail of Visible luminescence study of the infrared multiphoton dissociation of 2-chloroethenylsilane

Journal of Photochemistry and Photobiology A-chemistry, 1997

Research paper thumbnail of Real time study of the infrared multiphoton dissociation of vinylbromide

Journal of Photochemistry and Photobiology A-chemistry, 1999

... a Instituto de Estructura de la Materia, CSIC, Serrano 121, 28006 Madrid, Spain. b Instituto ... more ... a Instituto de Estructura de la Materia, CSIC, Serrano 121, 28006 Madrid, Spain. b Instituto de Química-Fisica 'Roca Solano', CSIC, Serrano 119, 28006 Madrid, Spain. Accepted 29 March 1999. Available online 10 August 1999. Abstract. ...

Research paper thumbnail of Collisionally Induced Bottleneck Weakening in IR Multiphoton Dissociation

The Journal of Physical Chemistry, 1996

... the ratio of the pulse energy, measured with a Lumonics 20D pyroelectric detector, and the “1... more ... the ratio of the pulse energy, measured with a Lumonics 20D pyroelectric detector, and the “1/e” cross-sectional beam area measured at the cell position with a pyroelectric detector array Delta Development Mark IV (these ... Tosa, V.; Bruzzese, R.; De Lisio, C.; Solimeno, S. J. Mol. ...

Research paper thumbnail of Laser induced fluorescence detection of CF, CF 2 and CF 3 in the infrared multiphoton dissociation of C 3F 6

Journal of Photochemistry and Photobiology A-chemistry, 2001

The infrared multiphoton dissociation of C 3 F 6 has been studied through the analysis of the las... more The infrared multiphoton dissociation of C 3 F 6 has been studied through the analysis of the laser induced fluorescence of the produced CF, CF 2 and CF 3 radicals. The influence of buffer gases in the process has also been investigated. In the studied conditions, only unimolecular formation of these radicals has been detected. A discussion about the possible dissociation channels has been done. The obtained excitation spectra show that CF 2 is formed vibrationally hot and reveal the presence of the radical CF 3 . From the analysis of these spectra, different values of the vibrational temperature are obtained, for the two experimental employed arrangements.

Research paper thumbnail of Ética na Administração de Materiais

A ética nas organizações pode ser percebida como um valor que faz com que a organização assegure ... more A ética nas organizações pode ser percebida como um valor que faz com que a organização assegure sua reputação e sobrevivência e em consequência disso resguarde seus bons resultados.

Research paper thumbnail of IR laser-induced process for chemical vapor deposition of polyselenocarbosilane films

Journal of Analytical and Applied Pyrolysis, 2006

TEA CO2 laser irradiation into gaseous mixtures of 1,3-disilacyclobutane (DSCB) and dimethyl sele... more TEA CO2 laser irradiation into gaseous mixtures of 1,3-disilacyclobutane (DSCB) and dimethyl selenide (DMS) results in infrared multiple photon-induced, non-interacting homogeneous decompositions of both educts, one yielding silene (H2SiCH2) and the other elemental selenium as major products. The reaction between polymerizing silene and agglomerizing Se leads to chemical vapor deposition of novel polyselenocarbosilane films which are unstable in atmosphere. The

Research paper thumbnail of IR laser-induced co-decomposition of dimethyl selenide and trisilane: Gas-phase formation of SiSe and chemical vapor deposition of nanostructured H/Si/Se/C polymers

Journal of Photochemistry and Photobiology A-chemistry, 2007

Chemical changes in IR laser irradiated gaseous mixtures of dimethyl selenide and trisilane have ... more Chemical changes in IR laser irradiated gaseous mixtures of dimethyl selenide and trisilane have been diagnosed by laser-induced fluorescence (LIF) of transient species and by FTIR, Raman, photoelectron spectroscopy and electron microscopy of the final solid products deposited from the gas phase. It is revealed that decomposition of both compounds leads to gas-phase formation of SiSe and deposition of solid nanostructured polymeric materials. We present indirect evidence on the presence of Si Se bonds in these polymers by revealing that these polymers undergo hydrolysis in air to H 2 Se and CH 3 SeH, which converts them to solid silicone-based films containing elemental selenium. Plausible reactions taking place in the gas phase and upon exposure of solids to air are suggested.

Research paper thumbnail of Infrared laser-induced chemistry of chlorodifluoromethane?silane mixtures at two irradiating wavelengths

Journal of The Chemical Society, Faraday Transactions, 1993

... irradiating line [fluence/J cm-,] energy absorbed" (YO) 9R(34) C2.61 + lOP(20) [1.4] 9P(... more ... irradiating line [fluence/J cm-,] energy absorbed" (YO) 9R(34) C2.61 + lOP(20) [1.4] 9P(34)Cl.51 + lOP(20) C1.31 lOP(20) [ 1.41 lOP(20) C1.8) + lOP(20) c1.4) 9P(34) C2.1) 20-2 1 24-26 21 3b With time delay 0-1 ps. No decomposition. wavelengths experiments. ...

Research paper thumbnail of Gas-phase formation of SiSe in IR laser-co-decomposition of dimethyl selenide and 1,3-disilacyclobutane

Journal of Organometallic Chemistry, 2007

A LIF excitation spectrum of SiSe obtained upon IR laser irradiation of gaseous mixture of 1,3-di... more A LIF excitation spectrum of SiSe obtained upon IR laser irradiation of gaseous mixture of 1,3-disilacyclobutane and dimethyl selenide reveals that the previously reported infrared multiple photon co-decomposition of both compounds involves formation of SiSe. The SiSe formation is explained in terms of reaction of Se atoms with RHSi: silylenes (R = CH 3 , H) and silene, and elimination of RH from silaneselones (RHSiSe, R = CH 3 , H).

Research paper thumbnail of IR laser-induced thermolysis of (chloromethyl)silane: complex reaction involving H2Si:, H2C: and HClSi: transients and yielding nanostructured Si/C/H phases

Journal of Materials Chemistry, 2002

Page 1. IR laser-induced thermolysis of (chloromethyl)silane: complex reaction involving H2Si:, H... more Page 1. IR laser-induced thermolysis of (chloromethyl)silane: complex reaction involving H2Si:, H2C: and HClSi: transients and yielding nanostructured Si/C/H phases Josef Pola,*a Magna Santos,b Luis Dıaz,b Kristýna Jursıková ...

Research paper thumbnail of Silicon Oxide Cluster Formation and Stability in the Laser Ablation of SiO Targets

Journal of Physical Chemistry A, 2009

The formation mechanism and stability of silicon oxide clusters observed in the ablation of SiO t... more The formation mechanism and stability of silicon oxide clusters observed in the ablation of SiO targets at 266 nm were investigated by time-of-flight mass spectrometry, laser-induced fluorescence (LIF), and DFT calculations. Neutral and positively charged Sin+/0 and SinOmH0,1+ clusters were identified in the plume, but neutral SinOm could not be observed. The time distribution of SiO in the plume measured by postionization with an ArF laser (Δλ ≈ 1 nm, τ ≈ 14 ns) and mass spectrometric detection was compared with that obtained by LIF with narrowband dye laser selective excitation of one specific rovibronic transition in SiO. Postionization leads to a multicomponent distribution that extends up to times near 100 μs after ablation, whereas LIF measurements obtain time distributions shorter than 20 μs. DFT calculations of several SinOm0/+ were performed, showing that one photon absorption of the postionization laser makes available low-energy dissociation channels of the neutrals, whereas two photon absorption is required for ionization. DFT calculations were carried out for stoichiometric H-containing clusters SinOnH+ (n = 1-4). For n = 1,2, the optimized geometries involve bonding of hydrogen to one oxygen atom in the clusters; for n = 3 and 4, the structures containing H-Si bonds are more stable.

Research paper thumbnail of IR laser-induced decomposition of 2-chloroethenylsilane for chemical vapour deposition of Si/C phases

Journal of Materials Chemistry, 1996

Infrared multiphoton decomposition of 2-chloroethenylsilane is dominated by dehydrochlorination a... more Infrared multiphoton decomposition of 2-chloroethenylsilane is dominated by dehydrochlorination and by decomposition of the intermediary ethynylsilane, and it affords a solid material consisting of an Si/C/H polymer and silicon carbide. The content of the latter ...

Research paper thumbnail of Plume investigations of the mechanisms of SiO laser ablation at 266 nm

Journal of Physics: Conference Series, 2007

The ablation mechanism of SiO at the laser wavelength of 266 nm has been investigated by characte... more The ablation mechanism of SiO at the laser wavelength of 266 nm has been investigated by characterizing the composition and dynamics of neutral and charged particles produced in the ablation. The neutral and ionized composition of the plume and the dynamics of neutral SiO were investigated by time-of-flight mass spectrometry. The velocity distribution of neutral SiO molecules shows contributions of slow and fast components. The velocity distributions of charged species in the plume were investigated by a Langmuir probe technique, obtaining that the distributions shift towards higher velocities with increasing distance from the target surface. The fastest component of the velocity distribution of neutral SiO overlaps the slowest part of the velocity distribution of charged species. The average rotational energy of SiO molecules, estimated by LIF spectroscopy does not allow to draw clear conclusions about the participation of silicon oxide ion clusters as the precursors of fast SiO molecules in the plume.

Research paper thumbnail of IR and UV laser-induced photolysis of 2-chloroethenylsilane

Journal of Photochemistry and Photobiology A-chemistry, 1997

The laser-induced decomposition of 2-chloroethenylsilane was studied in the IR with a TEA CO 2 la... more The laser-induced decomposition of 2-chloroethenylsilane was studied in the IR with a TEA CO 2 laser and in the UV with a narrow-band, frequency-doubled dye laser at 212.5 nm. Silylene was observed in the IR multiphoton dissociation (MPD) via laser-induced fluorescence ...

Research paper thumbnail of IR laser-induced chemical vapor deposition of carbon-coated iron nanoparticles embedded in polymer

Journal of Materials Chemistry, 2005

Co-decomposition of gaseous mixtures of silacyclopent-3-ene and Fe (CO) 5 by irradiation at (9+ 1... more Co-decomposition of gaseous mixtures of silacyclopent-3-ene and Fe (CO) 5 by irradiation at (9+ 10) and (9+ 10+ 5) µm from two CO 2 lasers is reported. In a one-step process, this produced nanosized (α-Fe)-based particles that consist of both superparamagnetic and ...

Research paper thumbnail of IR laser-induced co-decomposition of trisilane and thiirane for deposition of polycarbosilthiane films

Journal of Analytical and Applied Pyrolysis, 2008

ABSTRACT TEA CO2 laser irradiation of gaseous trisilane–thiirane mixtures results in the co-decom... more ABSTRACT TEA CO2 laser irradiation of gaseous trisilane–thiirane mixtures results in the co-decomposition of both components and allows chemical vapor deposition of polycarbosilthiane films that undergo reaction with air moisture, evolve H2S and develop to polycarbosiloxanes. Laser-induced fluorescence experiments allowed detection of transient SiS in the gas phase. The gas-phase formation of SiS and polycarbosilthiane, accounted for on the basis GC/MS analysis of final volatile products and in situ measured FTIR spectra of the deposited polymers, involves reactions between silylenes and S atoms that are respective intermediates of trisilane and thiirane decomposition.

Research paper thumbnail of IR laser-induced thermolysis of silacyclopent-3-ene: extrusion of silylene and chemical vapour deposition of polycarbosilane phases via reactions of silylene, buta-1,3-diene and methylene

Journal of Organometallic Chemistry, 2000

Infrared laser-induced (SF 6 ) photosensitized decomposition and infrared laser multiphoton decom... more Infrared laser-induced (SF 6 ) photosensitized decomposition and infrared laser multiphoton decomposition of silacyclopent-3ene occur as extrusion of silylene, yielding butadiene as a major gaseous product and affording chemical vapour deposition of solid saturated polycarbosilane films. The involvement of H 2 Si:, H 2 C: and buta-1,3-diene in the formation of the films is revealed through quantification of the gaseous products and identification of H 2 Si: and H 2 C: by laser induced fluorescence.

Research paper thumbnail of Silicon Oxide Cluster Formation and Stability in the Laser Ablation of SiO Targets

Journal of Physical Chemistry A, 2009

The formation mechanism and stability of silicon oxide clusters observed in the ablation of SiO t... more The formation mechanism and stability of silicon oxide clusters observed in the ablation of SiO targets at 266 nm were investigated by time-of-flight mass spectrometry, laser-induced fluorescence (LIF), and DFT calculations. Neutral and positively charged Si(n)(+/0) and Si(n)O(m)H(0,1)(+) clusters were identified in the plume, but neutral Si(n)O(m) could not be observed. The time distribution of SiO in the plume measured by postionization with an ArF laser (Delta lambda approximately 1 nm, tau approximately 14 ns) and mass spectrometric detection was compared with that obtained by LIF with narrowband dye laser selective excitation of one specific rovibronic transition in SiO. Postionization leads to a multicomponent distribution that extends up to times near 100 micros after ablation, whereas LIF measurements obtain time distributions shorter than 20 micros. DFT calculations of several Si(n)O(m)(0/+) were performed, showing that one photon absorption of the postionization laser makes available low-energy dissociation channels of the neutrals, whereas two photon absorption is required for ionization. DFT calculations were carried out for stoichiometric H-containing clusters Si(n)O(n)H(+) (n = 1-4). For n = 1,2, the optimized geometries involve bonding of hydrogen to one oxygen atom in the clusters; for n = 3 and 4, the structures containing H-Si bonds are more stable.

Research paper thumbnail of Transient detection in infrared multiphoton decomposition of (chloromethyl)silane and 1,3-disilacyclobutane: evidence for cleavage of SiCH 4 intermediates

Journal of Photochemistry and Photobiology A-chemistry, 2002

The transients produced in the infrared multiphoton decomposition (IRMPD) of (chloromethyl)silane... more The transients produced in the infrared multiphoton decomposition (IRMPD) of (chloromethyl)silane-HClSi:, H 2 Si: and H 2 C:-and of 1,3-disilacyclobutane-H 2 Si: and H 2 C:-have been identified by laser-induced fluorescence (LIF). The nascent HClSi: and H 2 Si: populations are generated with a high degree of excitation and the species produced from (chloromethyl)silane possess more rotational and vibrational energy than those produced from 1,3-disilacyclobutane. The obtained quenching rate and radiative lifetime for HClSi: are (4.6± 0.3) × 10 −10 cm 3 per molecule s −1 and 369 ± 10 ns, respectively. The formation of H 2 Si: and H 2 C: in IRMPD of both (chloromethyl)silane and 1,3-disilacyclobutane adds to previous knowledge on decomposition of (chloromethyl)silane and 1,3-disilacyclobutane and suggests that these transients are produced from the same SiCH 4 (H 3 Si(H)C: and (CH 3 )HSi:) intermediates.

Research paper thumbnail of Visible luminescence study of the infrared multiphoton dissociation of 2-chloroethenylsilane

Journal of Photochemistry and Photobiology A-chemistry, 1997

Research paper thumbnail of Real time study of the infrared multiphoton dissociation of vinylbromide

Journal of Photochemistry and Photobiology A-chemistry, 1999

... a Instituto de Estructura de la Materia, CSIC, Serrano 121, 28006 Madrid, Spain. b Instituto ... more ... a Instituto de Estructura de la Materia, CSIC, Serrano 121, 28006 Madrid, Spain. b Instituto de Química-Fisica 'Roca Solano', CSIC, Serrano 119, 28006 Madrid, Spain. Accepted 29 March 1999. Available online 10 August 1999. Abstract. ...

Research paper thumbnail of Collisionally Induced Bottleneck Weakening in IR Multiphoton Dissociation

The Journal of Physical Chemistry, 1996

... the ratio of the pulse energy, measured with a Lumonics 20D pyroelectric detector, and the “1... more ... the ratio of the pulse energy, measured with a Lumonics 20D pyroelectric detector, and the “1/e” cross-sectional beam area measured at the cell position with a pyroelectric detector array Delta Development Mark IV (these ... Tosa, V.; Bruzzese, R.; De Lisio, C.; Solimeno, S. J. Mol. ...

Research paper thumbnail of Laser induced fluorescence detection of CF, CF 2 and CF 3 in the infrared multiphoton dissociation of C 3F 6

Journal of Photochemistry and Photobiology A-chemistry, 2001

The infrared multiphoton dissociation of C 3 F 6 has been studied through the analysis of the las... more The infrared multiphoton dissociation of C 3 F 6 has been studied through the analysis of the laser induced fluorescence of the produced CF, CF 2 and CF 3 radicals. The influence of buffer gases in the process has also been investigated. In the studied conditions, only unimolecular formation of these radicals has been detected. A discussion about the possible dissociation channels has been done. The obtained excitation spectra show that CF 2 is formed vibrationally hot and reveal the presence of the radical CF 3 . From the analysis of these spectra, different values of the vibrational temperature are obtained, for the two experimental employed arrangements.

Research paper thumbnail of Ética na Administração de Materiais

A ética nas organizações pode ser percebida como um valor que faz com que a organização assegure ... more A ética nas organizações pode ser percebida como um valor que faz com que a organização assegure sua reputação e sobrevivência e em consequência disso resguarde seus bons resultados.