Person: Bañares Morcillo, Luis
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First Name
Luis
Last Name
Bañares Morcillo
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Químicas
Department
Química Física
Area
Química Física
Identifiers
12 results
Search Results
Now showing 1 - 10 of 12
Item A velocity map imaging study of the photodissociation of the à state of ammonia(Physical Chemistry Chemical Physics, 2014) Rodríguez, Javier ; González, Marta ; Rubio-Lago, Luis; Bañares Morcillo, LuisItem A slice imaging and multisurface wave packet study of the photodissociation of CH3I at 304 nm(Physical Chemistry Chemical Physics, 2011) Rubio-Lago, Luis; Rodríguez. Javier; García-Vela, Alberto; González, María; Amaral, Gabriel; Bañares Morcillo, LuisThe role of the conical intersection between the 1Q1 and 3Q0 excited states in the photodissociation of CH3I at 304 nm is investigated drawing a comparison between the adiabatic—through direct absorption to the 3Q1 state—and non-adiabatic—via the 1Q1 → 3Q0 conical intersection—production of I atoms in the ground 2P3/2 state. The versatility of the slice imaging technique in combination with resonance enhanced multiphoton ionization (REMPI) detection of I(2P3/2) atoms allow distinct measurements of the competing processes. The I(2P3/2) atom kinetic energy distributions (KEDs) obtained in both cases reflect inverted vibrational progressions of the ν2 umbrella mode of the CH3 co-product. The experimental results show a satisfactory agreement with multisurface wave packet calculations using a reduced dimensionality (pseudotriatomic) model carried out on the available ab initio potential energy surfacesItem Slice imaging and wave packet study of the photodissociation of CH3I in the blue edge of the A-band: evidence of reverse 3Q0←1Q1 non-adiabatic dynamics(Physical Chemistry Chemical Physics, 2011) González, María; Rodríguez, Javier; Rubio-Lago, Luis; García-Vela, Alberto; Bañares Morcillo, LuisItem Imaging the radical channel in acetaldehyde photodissociation: Competing mechanisms at energies close to the triplet exit barrier(2010) Amaral, Gabriel; Arregui, Andrés; Rubio-Lago, Luis; Rodríguez, Javier; Bañares Morcillo, LuisThe photodissociation of acetaldehyde in the radical channel has been studied at wavelengths between 315 and 325 nm using the velocity-map imaging technique. Upon one-photon absorption at 315 nm, the molecule is excited to the first singlet excited state S1, which, in turn, undergoes intersystem crossing to the first excited triplet state T1. On the triplet surface, the molecule dissociates into CH3 and HCO radicals with large kinetic energy release (KER), in accordance with the well characterized exit barrier on T1. However, at longer wavelengths (>320 nm), which correspond to excitation energies just below the triplet barrier, a sudden change in KER is observed. At these photolysis wavelengths, there is not enough energy to surpass the exit barrier on the triplet state, which leaves the possibility of unimolecular dissociation on S0 after internal conversion from S1. We have characterized the fragments’ KER at these wavelengths, as well as determined the energy partitioning for the radical fragments. A new accurate estimate of the barrier height on T1 is presented.Item Communication: First observation of ground state I(2P3/2) atoms from the CH3I photodissociation in the B-band(The Journal of Chemical Physics, 2011) González, María; Rodríguez, Javier; Rubio-Lago, Luis; Bañares Morcillo, LuisThe photodissociation of CH3I in the second absorption band (the B-band) has been studied at the wavelength 199.11 nm, coincident with the 31 0 3R1(E) ← X˜ (1A1) CH3I vibronic transition, using a combination of slice imaging and resonance enhanced multiphoton ionization detection of the CH3 fragment. The kinetic energy and angular distributions of the recoiling CH3 fragment confirm a major predissociation dynamics channel as a result of the interaction between the bound 3R1 Rydberg state and the repulsive 3A1(E) state − ascribed to the A-band − yielding CH3 fragments in correlation with spin-orbit excited I*(2P1/2) atoms. In addition, first evidence of a non-negligible population of ground state I(2P3/2) atoms in the CH3 fragment slice images, suggests a secondary predissociation mechanism via interaction between the 3R1 Rydberg state and the repulsive A-band 1Q1 state.Item Photodissociation dynamics of bromoiodomethane from the first and second absorption bands. A combined velocity map and slice imaging study(Physical Chemistry Chemical Physics, 2018) Marggi Poullaín, Sonia; Chicharro, David ; Navarro, Eduardo; Rubio-Lago, Luis; González-Vázquez, Jesús; Bañares Morcillo, LuisThe photodissociation dynamics of bromoiodomethane (CH2BrI) have been investigated at the maximum of the first A and second A′ absorption bands, at 266 and 210 nm excitation wavelengths, respectively, using velocity map and slice imaging techniques in combination with a probe detection of both iodine and bromine fragments, I(2P3/2), I*(2P1/2), Br(2P3/2) and Br*(2P1/2) via (2 + 1) resonance enhanced multiphoton ionization. Experimental results, i.e. translational energy and angular distributions, are reported and discussed in conjunction with high level ab initio calculations of potential energy curves and absorption spectra. The results indicate that in the A-band, direct dissociation through the 5A′ excited state leads to the I(2P3/2) channel while I*(2P1/2) atoms are produced via the 5A′ → 4A′/4A′′ nonadiabatic crossing. The presence of Br and Br* fragments upon excitation to the A-band is attributed to indirect dissociation via a curve crossing between the 5A′ with upper excited states such as the 9A′. The A′-band is characterized by a strong photoselectivity leading exclusively to the Br(2P3/2) and Br*(2P1/2) channels, which are likely produced by dissociation through the 9A′ excited state. Avoided crossings between several excited states from both the A and A′ bands entangle however the possible reaction pathways.Item Imaging the stereodynamics of methyl iodide photodissociation in the second absorption band: fragment polarization and the interplay between direct and predissociation(2014) González, Marta ; Rodríguez, Javier ; Rubio-Lago, Luis; Bañares Morcillo, LuisStereodynamics imaging disentangles the interplay between direct and predissociation in the onset of the second absorption band of methyl iodide.Item A velocity-map imaging study of the photodissociation of the methyl iodide cation(Physical Chemistry Chemical Physics, 2017) Marggi Poullaín, Sonia; Chicharro Vacas, David; Rubio-Lago, Luis; González-Vázquez, Jesús; Bañares Morcillo, LuisThe photodissociation dynamics of the methyl iodide cation has been studied using the velocity map imaging technique. A first laser pulse is used to ionize methyl iodide via a (2 + 1) REMPI scheme through the 5pp - 6p Rydberg state two-photon transition. The produced CH3I+(X) ions are subsequently excited at several wavelengths between 242 and 260 nm. The reported translational energy distributions for the methyl and iodine ions present a Boltzmann-type unstructured distribution at low excitation energies as well as a recoiled narrow structure at higher excitation energies highlighting two different dissociation processes. High level ab initio calculations have been performed in order to obtain a deeper understanding of the photodissociation dynamics of the CH3I+ ion. Direct dissociation on a repulsive state from the manifold of states representing the B˜ excited state leads to CH3+(X) + I*(2P1/2), while the CH3 + I+(3P2) channel is populated through an avoided crossing outside the Franck–Condon region. In contrast, an indirect process involving the transfer of energy from highly excited electronic states to the ground state of the ion is responsible for the observed Boltzmann-type distributions.Item Photodissociation of pyrrole-ammonia clusters below 218 nm: Quenching of statistical decomposition pathways under clustering conditions(The Journal of Chemical Physics, 2012) Rodríguez, Javier ; González, Miguel; Rubio-Lago, Luis; Bañares Morcillo, LuisThe excited state hydrogen transfer (ESHT) reaction in pyrrole-ammonia clusters (PyH·(NH3)n, n = 2–5) at excitation wavelengths below 218 nm down to 199 nm, has been studied using a combination of velocity map imaging and non-resonant detection of the NH4(NH3)n−1 products. Special care has been taken to avoid evaporation of solvent molecules from the excited clusters by controlling the intensity of both the excitation and probing lasers. The high resolution translational energy distributions obtained are analyzed on the base of an impulsive mechanism for the hydrogen transfer, which mimics the direct N−H bond dissociation of the bare pyrrole. In spite of the low dissociation wavelengths attained (∼200 nm) no evidence of hydrogen-loss statistical dynamics has been observed. The effects of clustering of pyrrole with ammonia molecules on the possible statistical decomposition channels of the bare pyrrole are discussedItem Site-specific hydrogen-atom elimination in photoexcited ethyl radical(Chemical Science, 2019) Chicharro Vacas, David; Marggi Poullaín, Sonia; Zanchet, Alexandre; Bouallagui, Aymen; García-Vela, Alberto; Senent, María ; Rubio-Lago, Luis; Bañares Morcillo, LuisThe photochemistry of the ethyl radical following excitation to the 3p Rydberg state is investigated in a joint experimental and theoretical study. Velocity map images for hydrogen atoms detected from photoexcited isotopologues CH3CH2, CH3CD2 and CD3CH2 at 201 nm, are discussed along with high-level ab initio electronic structure calculations of potential energy curves and non-adiabatic coupling matrix elements (NACME). A novel mechanism governed by a conical intersection allowing prompt site-specific hydrogen-atom elimination is presented and discussed. For this mechanism to occur, an initial rovibrational excitation is allocated to the radical permitting to access this reaction pathway and thus to control the ethyl photochemistry. While hydrogen-atom elimination from cold ethyl radicals occurs through internal conversion into lower electronic states followed by slow statistical dissociation, prompt site-specific Ca elimination into CH3CH + H, occurring through a fast non-adiabatic crossing to a valence bound state followed by dissociation through a conical intersection, is accessed by means of an initial ro-vibrational energy content into the radical. The role of a particularly effective vibrational promoting mode in this prompt photochemical reaction pathway is discussed.