A femtosecond velocity map imaging study on B-band predissociation in CH 3I. II. the 2 0 1 and 3 0 1 vibronic levels

Femtosecond time-resolved velocity map imaging experiments are reported on several vibronic levels of the second absorption band (B-band) of CH 3I, including vibrational excitation in the 2 and 3 modes of the bound 3R 1(E) Rydberg state. Specific predissociation lifetimes have been determined for the 201 and 301 vibronic levels from measurements of time-resolved I*( 2P 12) and CH 3 fragment images, parent decay, and photoelectron images obtained through both resonant and non-resonant multiphoton ionization. The results are compared with our previously reported predissociation lifetime measurements for the band origin 000 [Gitzinger, J. Chem. Phys. 132, 234313 (2010)10.1063/1.3455207]. The result, previously reported in the literature, where vibrational excitation to the C-I stretching mode ( 3) of the CH 3I 3R 1(E) Rydberg state yields a predissociation lifetime about four times slower than that corresponding to the vibrationless state, whereas predissociation is twice faster if the vibrational excitation is to the umbrella mode ( 2), is confirmed in the present experiments. In addition to the specific vibrational state lifetimes, which were found to be 0.85 0.04 ps and 4.34 0.13 ps for the 201 and 301 vibronic levels, respectively, the time evolution of the fragment anisotropy and the vibrational activity of the CH 3 fragment are presented. Additional striking results found in the present work are the evidence of ground state I( 2P 32) fragment production when excitation is produced specifically to the 301 vibronic level, which is attributed to predissociation via the A-band 1Q 1 potential energy surface, and the indication of a fast adiabatic photodissociation process through the repulsive A-band 3A 1(4E) state, after direct absorption to this state, competing with absorption to the 301 vibronic level of the 3R 1(E) Rydberg state of the B-band.Peer Reviewe

Synthetic Biology: Mapping the Scientific Landscape

This article uses data from Thomson Reuters Web of Science to map and analyse the scientific landscape for synthetic biology. The article draws on recent advances in data visualisation and analytics with the aim of informing upcoming international policy debates on the governance of synthetic biology by the Subsidiary Body on Scientific, Technical and Technological Advice (SBSTTA) of the United Nations Convention on Biological Diversity. We use mapping techniques to identify how synthetic biology can best be understood and the range of institutions, researchers and funding agencies involved. Debates under the Convention are likely to focus on a possible moratorium on the field release of synthetic organisms, cells or genomes. Based on the empirical evidence we propose that guidance could be provided to funding agencies to respect the letter and spirit of the Convention on Biological Diversity in making research investments. Building on the recommendations of the United States Presidential Commission for the Study of Bioethical Issues we demonstrate that it is possible to promote independent and transparent monitoring of developments in synthetic biology using modern information tools. In particular, public and policy understanding and engagement with synthetic biology can be enhanced through the use of online interactive tools. As a step forward in this process we make existing data on the scientific literature on synthetic biology available in an online interactive workbook so that researchers, policy makers and civil society can explore the data and draw conclusions for themselves

A femtosecond velocity map imaging study on B -band predissociation in CH3 I. I. the band origin

7 p.; 5 fig.; 1 tab.A femtosecond pump-probe experiment, coupled with velocity map ion imaging, is reported on the second absorption band (B -band) of CH3 I. 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 (2) and the symmetric stretch (1) 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. © 2010 American Institute of Physics.We thank Dr. Alberto García-Vela and Dr. Jesús González Vázquez for fruitful discussions. M.E.C. acknowledges financial support from MICINN Spain through a FPU fellowship. This work has been financed by the Spanish MICINN through Grant No. CTQ2008-02578/BQU, the Consolider program “Science and Applications of Ultrafast Ultraintense Lasers,” Grant No. CSD2007-00013, and by the European Union ITN network “Ultrafast control of quantum systems by strong laser fields—FASTQUAST” Grant No. PITN-GA-2008-214962. This research has been performed within the Unidad Asociada “Química Física Molecular” between Departamento de Química Física of UCM and CSIC. The facilities provided by the Centro de Asistencia a la Investigación de Espectroscopia Multifotónica y de Femtosegundo UCM are gratefully acknowledged

Pulse shaping control of CH3 i multiphoton ionization at 540 nm

A pulse shaping control experiment on multiphoton ionization of the methyl iodide (CH3I) molecule is reported. A range of phase masks were applied in the Fourier plane of a 4f pulse shaper containing a spatial light modulator, causing spectro-temporal modulation in the 540 nm pulses synthesized in an optical parametric amplifier. The ionization process was studied through velocity map imaging of outgoing photoelectrons. Four main ionization channels were identified, with relative yields that are dependent on the pulse shape applied, indicating that the ionization routes can be steered through light manipulation to some extent. The main mechanism for control seems to derive from peak intensity effects, but some features observed in the photoelectron spectra defy this explanation. The role of resonances at the three-photon level is discussed. © 2014 Taylor and Francis.Peer Reviewe

Strong field control of predissociation dynamics

J2IFAM 2013 Madrid, February, 13rd-15th 2013Peer reviewe

Time-resolved alignment effects in CH_3I predissociation

Peer Reviewe

Velocity Map Imaging and Theoretical Study of the Coulomb Explosion of CH3I under Intense Femtosecond IR Pulses

Peer Reviewe

Dynamic Stark shift of the 3R1 Rydberg state of CH3I

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

A femtosecond velocity map imaging study on B

Femtosecond time-resolved velocity map imaging experiments are reported on several vibronic levels of the second absorption band (B-band) of CH 3I, including vibrational excitation in the 2 and 3 modes of the bound 3R 1(E) Rydberg state. Specific predissociation lifetimes have been determined for the 201 and 301 vibronic levels from measurements of time-resolved I*( 2P 12) and CH 3 fragment images, parent decay, and photoelectron images obtained through both resonant and non-resonant multiphoton ionization. The results are compared with our previously reported predissociation lifetime measurements for the band origin 000 [Gitzinger, J. Chem. Phys. 132, 234313 (2010)10.1063/1.3455207]. The result, previously reported in the literature, where vibrational excitation to the C-I stretching mode ( 3) of the CH 3I 3R 1(E) Rydberg state yields a predissociation lifetime about four times slower than that corresponding to the vibrationless state, whereas predissociation is twice faster if the vibrational excitation is to the umbrella mode ( 2), is confirmed in the present experiments. In addition to the specific vibrational state lifetimes, which were found to be 0.85 0.04 ps and 4.34 0.13 ps for the 201 and 301 vibronic levels, respectively, the time evolution of the fragment anisotropy and the vibrational activity of the CH 3 fragment are presented. Additional striking results found in the present work are the evidence of ground state I( 2P 32) fragment production when excitation is produced specifically to the 301 vibronic level, which is attributed to predissociation via the A-band 1Q 1 potential energy surface, and the indication of a fast adiabatic photodissociation process through the repulsive A-band 3A 1(4E) state, after direct absorption to this state, competing with absorption to the 301 vibronic level of the 3R 1(E) Rydberg state of the B-band.Peer Reviewe