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
9 results
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Now showing 1 - 9 of 9
Item Femtochemistry under scrutiny: Clocking state-resolved channels in the photodissociation of CH3I in the A-band(The Journal of Chemical Physics, 2020) Murillo Sánchez, Marta Luisa; González Vázquez, Jesús; Corrales Castellanos, María Eugenia; Nalda Míguez, Rebeca de; Martínez Núñez, Emilio; García Vela, Alberto; Bañares Morcillo, LuisClocking of electronically and vibrationally state-resolved channels of the fast photodissociation of CH3I in the A-band is re-examined in a combined experimental and theoretical study. Experimentally, a femtosecond pump-probe scheme is employed in the modality of resonant probing by resonance enhanced multiphoton ionization (REMPI) of the methyl fragment in different vibrational states and detection through fragment velocity map ion (VMI) imaging as a function of the time delay. We revisit excitation to the center of the A-band at 268 nm and report new results for excitation to the blue of the band center at 243 nm. Theoretically, two approaches have been employed to shed light into the observations: first, a reduced dimensionality 4D nonadiabatic wavepacket calculation using the potential energy surfaces by Xie et al. [J. Phys. Chem. A 104, 1009 (2000)]; and second, a full dimension 9D trajectory surface-hopping calculation on the same potential energy surfaces, including the quantization of vibrational states of the methyl product. In addition, high level ab initio electronic structure calculations have been carried out to describe the CH3 3pz Rydberg state involved in the (2 + 1) REMPI probing process, as a function of the carbon-iodine (C–I) distance. A general qualitative agreement is obtained between experiment and theory, but the effect of methyl vibrational excitation in the umbrella mode on the clocking times is not well reproduced. The theoretical results reveal that no significant effect on the state-resolved appearance times is exerted by the nonadiabatic crossing through the conical intersection present in the first absorption band. The vibrationally state resolved clocking times observed experimentally can be rationalized when the (2 + 1) REMPI probing process is considered. None of the other probing methods applied thus far, i.e., multiphoton ionization photoelectron spectroscopy, soft X-ray inner-shell photoelectron spectroscopy, VUV single-photon ionization, and XUV core-to-valence transient absorption spectroscopy, have been able to provide quantum state-resolved (vibrational) clocking times. More experiments would be needed to disentangle the fine details in the clocking times and dissociation dynamics arising from the detection of specific quantum-states of the molecular fragments.Item Femtosecond time-resolved photophysics and photodissociation dynamics of 1-iodonaphthalene(Physical Chemistry Chemical Physics, 2010) Montero Gilete, Raul; Peralta Conde, Alvaro; Longarte Aldama, Asier; Almendral Castaño, Fernando; Corrales Castellanos, María Eugenia; Nalda Míguez, Rebeca de; Bañares Morcillo, LuisThe ultrafast relaxation of 1-iodonaphthalene, with particular attention to the dissociation channels, has been studied by time-resolved femtosecond pump–probe mass spectrometry following excitation at 267 and 317 nm. The measured transients for the parent ion and the isobaric fragments, iodine and naphthyl radical, show complex decay profiles with up to four lifetimes in the femto-picosecond time scales. The transients are interpreted as the result of parallel relaxation of the simultaneously excited nσ* and ππ* states of the molecule. While the former leads to dissociation in about 400 fs, the latter converts to lower energy ππ* singlet states at an ultrafast rate (24 fs) followed by intersystem crossing to nearby ππ* triplet states.Item Substituent effects on nonadiabatic excited state dynamics: Inertial, steric, and electronic effects in methylated butadienes(The Journal of Chemical Physics, 2020) MacDonell, Ryan ; Corrales Castellanos, María Eugenia; Boguslavskiy, Andrey ; Bañares Morcillo, Luis; Stolow, Albert; Schuurman, MichaelThe photochemical dynamics of double-bond-containing hydrocarbons is exemplified by the smallest alkenes, ethylene and butadiene. Chemical substituents can alter both decay timescales and photoproducts through a combination of inertial effects due to substituent mass, steric effects due to substituent size, and electronic (or potential) effects due to perturbative changes to the electronic potential energy surface. Here, we demonstrate the interplay of different substituent effects on 1,3-butadiene and its methylated derivatives using a combination of ab initio simulation of nonadiabatic dynamics and time-resolved photoelectron spectroscopy. The purely inertial effects of methyl substitution are simulated through the use of mass 15 “heavy-hydrogen” atoms. As expected from both inertial and electronic influences, the excited-state dynamics is dominated by pyramidalization at the unsubstituted carbon sites. Although the electronic effects of methyl group substitution are weak, they alter both decay timescales and branching ratios by influencing the initial path taken by the excited wavepacket following photoexcitation.Item A femtosecond velocity map imaging study on B-band predissociation in CH3I. I. The band origin(The Journal of Chemical Physics, 2010) Gitzinger, Gregory; Corrales Castellanos, María Eugenia; Loriot, Vincent; Amaral Mathon, Gabriel; Nalda Míguez, Rebeca de; Bañares Morcillo, LuisA femtosecond pump-probe experiment, coupled with velocity map ion imaging, is reported on the second absorption band (B-band) of CH3I. The measurements provide a detailed picture of real-time B-band predissociation in the band origin at 201.2 nm. Several new data are reported. (i) A value of 1.5±0.1 ps has been obtained for the lifetime of the excited state, consistent within errors with the only other direct measurement of this quantity [A. P. Baronavski and J. C. Owrutsky, J. Chem. Phys. 108, 3445 (1998)]. (ii) It has been possible to measure the angular character of the transition directly through the observation of fragments appearing early with respect to both predissociation lifetime and molecular rotation. (iii) Vibrational activity in CH3 has been found, both in the umbrella (ν2) and the symmetric stretch (ν1) modes, with estimates of relative populations. All these findings constitute a challenge and a test for much-wanted high level ab initio and dynamics calculations in this energy region.Item Halogen-atom effect on the ultrafast photodissociation dynamics of the dihalomethanes CH2 ICl and CH2 BrI(Physical Chemistry Chemical Physics, 2018) Murillo Sánchez, Marta Luisa; Marggi Poullaín, Sonia; Bajo González, Juan José; Corrales Castellanos, María Eugenia; González Vázquez, Jesús; Sola Reija, Ignacio; Bañares Morcillo, LuisReal time photodissociation of dihalomethanes has been measured by femtosecond velocity map imaging to disentangle the effect of the halogen-atom on the carbon–iodine cleavage dynamics.Item Femtosecond XUV induced dynamics of the methyl iodide cation(2019) Reitsma, Geert; Murillo Sánchez, Marta Luisa; Nalda Míguez, Rebeca de; Corrales Castellanos, María Eugenia; Marggi Poullaín, Sonia; González Vázquez, Jesús; Vrakking, Marc ; Bañares Morcillo, Luis; Kornilov, OlegUltrashort XUV wavelength-selected pulses obtained with high harmonic generation are used to study the dynamics of molecular cations with state-to-state resolution. We demonstrate this by XUV pump - IR probe experiments on CH3I+ cations and identify both resonant and non-resonant dynamics.Item Velocity Map Imaging and Theoretical Study of the Coulomb Explosion of CH3I under Intense Femtosecond IR Pulses(The Journal of Physical Chemistry A, 2011) Corrales Castellanos, María Eugenia; Gitzinger, Gregory; González Vázquez, Jesús; Loriot, Vincent; Nalda Míguez, Rebeca de; Bañares Morcillo, LuisThe Coulomb explosion of CH3Iinanintense(10 100 TW cm 2),ultrashort (50 fs) and nonresonant (804 nm) laserfield has been studied ex-perimentally and justified theoretically. Ion imageshave been recorded using thevelocity map imaging (VMI) technique for different singly and multiply charged ionfragments, CH3p+(p=1)andIq+(qe3), arising from different Coulomb explosionchannels. The fragment kinetic energy distributions obtained from the measuredimages for these ion fragments show significantly lower energies than those expectedconsidering only Coulomb repulsion forces. The experimental results have beenrationalized in terms of one-dimensional wave packet calculations on ab initiopotential energy curves of the different multiply charged species. The calculationsreveal the existence of a potential energy barrier due to a bound minimum in thepotential energy curve of the CH3I2+species and a strong stabilization with respect tothe pure Coulombic repulsion for the higher charged CH3In+(n=3,4)species.Item Dynamic Stark shift of the 3R1 Rydberg state of CH3I(2013) Balerdi Villanueva, Garikoitz; Corrales Castellanos, María Eugenia; Gitzinger, Gregory; González Vázquez, Jesús; Sola Reija, Ignacio; Loriot, Vicent; Nalda Míguez, Rebeca de; Bañares Morcillo, Luis; Chergui, M.; Taylor, A.; Cundiff, S.; Vivie-Riedle, R. de; Yamagouchi, K.Stark shift of the 3R1 Rydberg state of CH3I is measured for different Stark field intensities. Photodissociation products, generated after predissociation of the state, were detected when the molecules were excited with photons resonant with the energy difference between the ground and the shifted 3R1 state, allowing the shift to be quantified. Qualitative agreement has been found with a 1D model.Item Femtosecond XUV induced dynamics of the methyl iodide cation(2019) Reitsma, Geert; Murillo Sánchez, Marta Luisa; Nalda Míguez, Rebeca de; Corrales Castellanos, María Eugenia; Marggi Poullaín, Sonia; González Vázquez, Jesús; Vrakking, Marc J.J.; Bañares Morcillo, Luis; Kornilov, Oleg; Cerullo, G.; Ogilvie, J.; Kärtner, F.; Khalil, M.; Li, R.Ultrashort XUV wavelength-selected pulses obtained with high harmonic generation are used to study the dynamics of molecular cations with state-to-state resolution. We demonstrate this by XUV pump - IR probe experiments on CH3I+ cations and identify both resonant and non-resonant dynamics.