scholarly journals Towards controlling the dissociation probability by light-induced conical intersections

2016 ◽  
Vol 194 ◽  
pp. 479-493 ◽  
Author(s):  
András Csehi ◽  
Gábor J. Halász ◽  
Lorenz S. Cederbaum ◽  
Ágnes Vibók
Keyword(s):  
Laser Intensity ◽  
Laser Pulses ◽  
Laser Frequency ◽  
Chem Phys ◽  
Conical Intersections ◽  
Dissociation Process ◽  
Nonadiabatic Coupling ◽  
Dissociation Probability ◽  
Vibrational Levels ◽  
The Impact

Light-induced conical intersections (LICIs) can be formed both by standing or by running laser waves. The position of a LICI is determined by the laser frequency while the laser intensity controls the strength of the nonadiabatic coupling. Recently, it was shown within the LICI framework that linearly chirped laser pulses have an impact on the dissociation dynamics of the D2+molecule (J. Chem. Phys.,143, 014305, (2015);J. Chem. Phys.,144, 074309, (2016)). In this work we exploit this finding and perform calculations using chirped laser pulses in which the time dependence of the laser frequency is designed so as to force the LICI to move together with the field-free vibrational wave packet as much as possible. Since nonadiabaticity is strongest in the vicinity of the conical intersection, this is the first step towards controlling the dissociation processviathe LICI. Our showcase example is again the D2+molecular ion. To demonstrate the impact of the LICIs on the dynamical properties of diatomics, the total dissociation probabilities and the population of the different vibrational levels after the dissociation process are studied and discussed.

Dynamics of water dimer in femtosecond laser pulses: a simulation study

2014 ◽  
Vol 28 (22) ◽  
pp. 1450179
Author(s):  
Zhiping Wang ◽  
Fengshou Zhang ◽  
Xuefeng Xu ◽  
Yanbiao Wang ◽  
Chaoyi Qian
Keyword(s):  
Local Density ◽  
General Pattern ◽  
Laser Pulses ◽  
Laser Frequency ◽  
Femtosecond Laser Pulses ◽  
Water Dimer ◽  
Intense Laser ◽  
Intense Laser Pulses ◽  
Typical Sequence ◽  
The Impact

In this paper, we study the electronic and ionic dynamics of the water dimer subject to short and intense laser pulses. The dynamics is described by means of the time-dependent local-density approximation coupled to ionic molecular dynamics (TDLDA-MD) non-adiabatically. The impact of laser frequency on the response of water dimer is discussed by exploring the ionization, the dipole signal and bond lengths of water dimer. Furthermore, it is found that the water donor is more sensitive to the laser field than the water acceptor and the probabilities for the ionic states show the general pattern of the typical sequence of the interlaced production maxima.

Molecules in strong laser fields: vibrational inversion and harmonic generation

1994 ◽  
Vol 72 (3) ◽  
pp. 673-677 ◽  
Author(s):  
Eric E. Aubanel ◽  
André D. Bandrauk
Keyword(s):  
Harmonic Generation ◽  
Laser Pulses ◽  
Harmonic Spectrum ◽  
Femtosecond Laser Pulses ◽  
Generation Process ◽  
High Order Harmonic Generation ◽  
Vibrationally Excited ◽  
Potential Wells ◽  
High Order Harmonic ◽  
Vibrational Levels

We examine two consequences of the unique behaviour of molecules in strong fields. First, by time gating of laser-induced avoided crossings with femtosecond laser pulses, one can obtain efficient vibrational inversion into a narrow distribution of vibrational levels of a molecular ion. We demonstrate this by numerical solution of the time-dependent Schrödinger equation for [Formula: see text] Second, we show results of numerical calculation with vibrationally excited [Formula: see text] of harmonic generation up to the 11th order of an intense 1064- nm laser. We predict that competition of photodissociation can be minimized by trapping the molecule in high-field-induced potential wells, thus enhancing the high-order harmonic generation process. Furthermore, the harmonic spectrum can serve as a measure of the structure of these laser-induced potentials.

scholarly journals Resolving the mesospheric nighttime 4.3 µm emission puzzle: comparison of the CO<sub>2</sub>(<i>ν</i><sub>3</sub>) and OH(<i>ν</i>) emission models

2017 ◽  
Vol 17 (16) ◽  
pp. 9751-9760 ◽  
Author(s):  
Peter A. Panka ◽  
Alexander A. Kutepov ◽  
Konstantinos S. Kalogerakis ◽  
Diego Janches ◽  
James M. Russell ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Vibrational Energy ◽  
Lower Thermosphere ◽  
Vibrational Energy Relaxation ◽  
Density Distributions ◽  
Direct Mechanism ◽  
Vibrational Levels ◽  
Emission Models ◽  
The Impact ◽  
Good Agreement

Abstract. In the 1970s, the mechanism of vibrational energy transfer from chemically produced OH(ν) in the nighttime mesosphere to the CO2(ν3) vibration, OH(ν) ⇒ N2(ν) ⇒ CO2(ν3), was proposed. In later studies it was shown that this "direct" mechanism for simulated nighttime 4.3 µm emissions of the mesosphere is not sufficient to explain space observations. In order to better simulate these observations, an additional enhancement is needed that would be equivalent to the production of 2.8–3 N2(1) molecules instead of one N2(1) molecule in each quenching reaction of OH(ν) + N2(0). Recently a new "indirect" channel of the OH(ν) energy transfer to N2(ν) vibrations, OH(ν) ⇒ O(1D) ⇒ N2(ν), was suggested and then confirmed in a laboratory experiment, where its rate for OH(ν = 9) + O(3P) was measured. We studied in detail the impact of the "direct" and "indirect" mechanisms on CO2(ν3) and OH(ν) vibrational level populations and emissions. We also compared our calculations with (a) the SABER/TIMED nighttime 4.3 µm CO2 and OH 1.6 and 2.0 µm limb radiances of the mesosphere–lower thermosphere (MLT) and (b) with ground- and space-based observations of OH(ν) densities in the nighttime mesosphere. We found that the new "indirect" channel provides a strong enhancement of the 4.3 µm CO2 emission, which is comparable to that obtained with the "direct" mechanism alone but assuming an efficiency that is 3 times higher. The model based on the "indirect" channel also produces OH(ν) density distributions which are in good agreement with both SABER limb OH emission observations and ground and space measurements. This is, however, not true for the model which relies on the "direct" mechanism alone. This discrepancy is caused by the lack of an efficient redistribution of the OH(ν) energy from higher vibrational levels emitting at 2.0 µm to lower levels emitting at 1.6 µm. In contrast, the new  indirect  mechanism efficiently removes at least five quanta in each OH(ν ≥ 5) + O(3P) collision and provides the OH(ν) distributions which agree with both SABER limb OH emission observations and ground- and space-based OH(ν) density measurements. This analysis suggests that the important mechanism of the OH(ν) vibrational energy relaxation in the nighttime MLT, which was missing in the emission models of this atmospheric layer, has been finally identified.

The impact of the retarded Kerr effect on the laser pulses’ propagation in air

2015 ◽  
Vol 69 (3) ◽  
Author(s):  
Le Wang ◽  
Cunliang Ma ◽  
Xiexing Qi ◽  
Wenbin Lin
Keyword(s):  
Kerr Effect ◽  
Laser Pulses ◽  
The Impact

scholarly journals Erratum: “What is the best semiclassical method for photochemical dynamics of systems with conical intersections?” [J. Chem. Phys. 109, 3321 (1998)]

1999 ◽  
Vol 110 (1) ◽  
pp. 687-688 ◽  
Author(s):  
Maria S. Topaler ◽  
Thomas C. Allison ◽  
David W. Schwenke ◽  
Donald G. Truhlar
Keyword(s):  
Chem Phys ◽  
Conical Intersections ◽  
Semiclassical Method

Potential energy curve of N2 revisited

2011 ◽  
Vol 76 (4) ◽  
pp. 327-341 ◽  
Author(s):  
Vladimír Špirko ◽  
Xiangzhu Li ◽  
Josef Paldus
Keyword(s):  
Potential Energy ◽  
Chem Phys ◽  
Nitrogen Molecule ◽  
Basis Set ◽  
Basis Sets ◽  
Energy Curve ◽  
Vibrational Levels ◽  
Complete Basis Set ◽  
State Potential ◽  
Excellent Description

Recently generated ground state potential energy curves (PECs) for the nitrogen molecule, as obtained with the reduced multireference (RMR) coupled-cluster (CC) method with singles and doubles (RMR-CCSD), and its version corrected for the secondary triples RMR-CCSD(T), using cc-pVXZ basis sets with X = D, T, and Q, as well as the extrapolated complete basis set (cbs) limit (X. Li and J. Paldus: J. Chem. Phys. 2008, 129, 054104), are compared with both the highly accurate theoretical configuration interaction PEC of Gdanitz (Chem. Phys. Lett. 1998, 283, 253) and analytic PECs obtained by fitting an extensive set of experimental data (R. J. Le Roy et al.: J. Chem. Phys. 2006, 125, 164310). These results are analyzed using a morphing procedure based on the reduced potential curve (RPC) method of Jenč. It is found that an RPC fit of both theoretical potentials can be achieved with only a few parameters. The RMR PECs are found to provide an excellent description of experimentally available vibrational levels, but significantly deviate from those of Gdanitz’s PEC for highly stretched geometries, yet still do provide a qualitatively correct PECs that lie within the region delimited by Le Roy’s analytical PECs.

scholarly journals Single-molecule imaging with longer X-ray laser pulses

IUCrJ ◽  
2015 ◽  
Vol 2 (6) ◽  
pp. 661-674 ◽  
Author(s):  
Andrew V. Martin ◽  
Justine K. Corso ◽  
Carl Caleman ◽  
Nicusor Timneanu ◽  
Harry M. Quiney
Keyword(s):  
Single Molecule ◽  
Laser Pulses ◽  
Bragg Diffraction ◽  
Single Molecule Imaging ◽  
X Ray ◽  
Damage Models ◽  
Statistical Fluctuations ◽  
Damage Processes ◽  
The Impact ◽  
Serial Femtosecond Crystallography

During the last five years, serial femtosecond crystallography using X-ray laser pulses has been developed into a powerful technique for determining the atomic structures of protein molecules from micrometre- and sub-micrometre-sized crystals. One of the key reasons for this success is the `self-gating' pulse effect, whereby the X-ray laser pulses do not need to outrun all radiation damage processes. Instead, X-ray-induced damage terminates the Bragg diffraction prior to the pulse completing its passage through the sample, as if the Bragg diffraction were generated by a shorter pulse of equal intensity. As a result, serial femtosecond crystallography does not need to be performed with pulses as short as 5–10 fs, but can succeed for pulses 50–100 fs in duration. It is shown here that a similar gating effect applies to single-molecule diffraction with respect to spatially uncorrelated damage processes like ionization and ion diffusion. The effect is clearly seen in calculations of the diffraction contrast, by calculating the diffraction of the average structure separately to the diffraction from statistical fluctuations of the structure due to damage (`damage noise'). The results suggest that sub-nanometre single-molecule imaging with 30–50 fs pulses, like those produced at currently operating facilities, should not yet be ruled out. The theory presented opens up new experimental avenues to measure the impact of damage on single-particle diffraction, which is needed to test damage models and to identify optimal imaging conditions.

scholarly journals Phase Coherence in Multiple Pulse Optical Spectroscopy

1983 ◽  
Vol 2 (2) ◽  
pp. 37-51 ◽  
Author(s):  
Warren S. Warren ◽  
Ahmed H. Zewail
Keyword(s):  
Optical Spectroscopy ◽  
Chem Phys ◽  
Detection Methods ◽  
Optical Transitions ◽  
Multiple Pulse ◽  
Pulse Trains ◽  
Multilevel Systems ◽  
Relaxation Parameters ◽  
Vibrational Levels ◽  
A New Technique

In this paper we describe a new technique for the generation of multiple pulse phase coherent sequences in optical spectroscopy. The technique is an extension of the acousto-optic modulation and fluorescence detection methods developed for optical transitions by Zewail and Orlowski (Zewail et al., Chem. Phys. Lett.48, 256 (1977); Orlowski et al., Chem. Phys. Lett.54, 197 (1978)). Application of these multiple pulse trains (of different phases) to optical transitions of two-level and multilevel systems is demonstrated experimentally. It is shown that they can be used to (i) suppress spontaneous emission background, (ii) enhance coherent transients such as photon echoes, (iii) measure additional relaxation parameters in systems with complex rotational-vibrational levels, and (iv) enhance the effective laser bandwidths through composite pulse trains, as demonstrated on I2 gas. Finally, the potential of this development is extended to the possibility of observing selective multiquantum excitation in molecules.

Aerosol pH and regime transition of sulfate formation in aerosol water during winter haze events in northern China

2020 ◽  
Author(s):  
Wei Tao ◽  
Hang Su ◽  
Guangjie Zheng ◽  
Jiandong Wang ◽  
Lixia Liu ◽  
...  
Keyword(s):  
Northern China ◽  
Chem Phys ◽  
Heterogeneous Reactions ◽  
Lower Atmosphere ◽  
Spatial And Temporal Variability ◽  
Oh Radicals ◽  
Night Time ◽  
Sulfate Formation ◽  
Iron Manganese ◽  
The Impact

&lt;p&gt;Understanding the formation mechanism of severe haze is crucial for the development of efficient pollution control strategy. Recently, multiphase reactions in aerosol water has been suggested as an important source of sulfate aerosol during severe haze (Zheng et al., 2015;Cheng et al., 2016). Though several oxidation mechanisms have been recognized, the dominant oxidation pathway is still under debate reflecting a missing consensus. Based on a model survey with Weather Research and Forecasting model coupled with Chemistry (WRF-Chem), we have investigated the variability of aerosol pH and regimes of sulfate formation through multiphase oxidation during the haze episodes in January of 2013. Our results show a large spatial and temporal variability in the aerosol pH and sulfate formation regimes. Surface aerosol pH shows a clear diurnal variation with low pH during daytime and high pH during night-time for most cases. Aerosol pH tends to decrease with increasing altitude in the lower atmosphere. For the scenario best reproduces the observations in Beijing, NO&lt;sub&gt;2&lt;/sub&gt;, TMI+O&lt;sub&gt;2&lt;/sub&gt;, O&lt;sub&gt;3&lt;/sub&gt; and H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt; pathways can all dominate the production of sulfate in specific areas of the Beijing-Tianjin-Hebei (BTH) region. With the increasing height, O&lt;sub&gt;3&lt;/sub&gt; pathway and gas phase oxidation by OH radicals become more important. Moreover, sensitivity tests also suggest that, emissions of crustal particles, NH&lt;sub&gt;3&lt;/sub&gt; and soluble iron/manganese have great impacts on aqueous phase chemistry, and should be better constrained in future studies.&lt;/p&gt;&lt;p&gt;References:&lt;/p&gt;&lt;p&gt;Zheng, G. J., Duan, F. K., Su, H., Ma, Y. L., Cheng, Y., Zheng, B., Zhang, Q., Huang, T., Kimoto, T., Chang, D., Poschl, U., Cheng, Y. F., and He, K. B.: Exploring the severe winter haze in Beijing: the impact of synoptic weather, regional transport and heterogeneous reactions, Atmos. Chem. Phys., 15, 2969-2983, 10.5194/acp-15-2969-2015, 2015.&lt;/p&gt;&lt;p&gt;Cheng, Y. F., Zheng, G. J., Wei, C., Mu, Q., Zheng, B., Wang, Z. B., Gao, M., Zhang, Q., He, K. B., Carmichael, G., Poschl, U., and Su, H.: Reactive nitrogen chemistry in aerosol water as a source of sulfate during haze events in China, Sci Adv, 2, e1601530, UNSP e1601530,10.1126/sciadv.1601530, 2016.&lt;/p&gt;

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