The kinetic‐energy‐releases (KER) distribution function of the fragment is an important observable in the molecular dynamics. In theory, there are several different methods to calculate the KER ...distribution function or spectrum, which could be generally divided into two classes: One is based on the analysis of the asymptotic wavepacket (“projection method”) and the other is on the analysis of the associated flux (“flux method”). By taking the above‐threshold dissociation of the HeH+ (v = 8) molecule as an example, we compared these two classes of methods. Based on evenly separated Fourier grid representation, the KER distribution calculated via the projection method FProj(Ek) is the same as the one calculated via the flux method FFlux(Ek). The relationship between FProj(Ek) and the distribution of the projection of the asymptotic wavepacket onto the energy eigenstates of the quasicontinuum, PProj(Ek), and the relationship between FFlux(Ek) and the distribution of the dissociation probability PFlux(Ek) from the cumulation of the associated flux, are determined.
The kinetic‐energy‐releases (KER) distribution of the fragments is one of the most important.
observables in experiment for us to understand the relevant molecular dynamics, such as the photodissociation, photoionization, or chemical reaction collision. By taking the above‐threshold dissociation of HeH+ (v = 8) as model, the projection method and the flux method for the calculation of KER distribution function F (E
k) have been compared.
So far, numerous researches on the He2H− system have still been restricted to several analytical forms of the potential energy interaction, where the calculations in the three‐body interaction may be ...not precise. With that in mind, we have provided an accurate, global, full‐dimensional potential energy surface (PES) for the ground state of the He2H− system by the fundamental invariant neural network (FI‐NN) fitting based on roughly 45 000 ab initio data points. The energy points are calculated with the coupled‐cluster singles and doubles with perturbative triples (CCSDT) method using the augmented Dunning‐type correlation‐consistent (aug‐cc‐pVTZ, aug‐cc‐pVQZ and aug‐cc‐pV5Z) basis sets, respectively. Based on adoption and comparison of three different extrapolation formulas, we obtained even accurate data points, which are extrapolated to the complete basis set (CBS) limit. The overall root mean square error of the fitting PES is only about 6.314 × 10−3 cm−1. It can be expected that this accurate PES would provide insights to further interesting discoveries in dynamics or spectroscopies for the relevant molecular systems.
The weak interaction of the He2 dimer, the HeH− anion and the He2H− trimer have recently attracted great attention due to its importance in the interstellar space. An accurate, global potential energy surface (PES) for the ground state of the He2H− system is constructed based on high‐level ab initio data points to the complete basis set (CBS) limit.
This work explores the role of geometric phase (GP), which results from light induced conical intersection (LICI), in photodissociation process of the D2+ molecule through solving the time‐dependent ...Schrödinger equation. The dissociation results between two cases including GP and excluding GP are compared. Different from the case including GP, the angular distribution of photofragments excluding GP is non‐vanishing at θ=π/2 which is the angle between the molecular axis and the polarization direction of laser field. Furthermore, in strong field, when the initial vibrational energy is higher than the energy of LICI point, not only the photofragments distributions present obvious quantum interference structures, but also the angular distributions of the photofragments of two cases have opposite oscillatory structure around θ=π/2. This also shows that the GP effect and nonadiabatic effect of LICI are unified in photodissociation processes.
The time‐independent Schrödinger equation is solved in two cases including GP and excluding GP for the D2+ molecule. In strong field, when the initial vibrational energy is higher than the energy of LICI point, not only the photofragments distributions present obvious quantum interference structures, but also the angular distribution of photofragments excluding GP is nonvanishing around θ=π/2. We show that the GP effect and nonadiabatic effect of LICI are unified in photodissociation processes.
Roaming is a novel mechanism in reaction dynamics. It describes an unusual pathway, which can be quite different from the conventional minimum-energy path, leading to products. While roaming has been ...reported or suggested in a number of unimolecular reactions, it has been rarely reported for bimolecular reactions. Here, we report a high-level computational study of roaming dynamics in the important bimolecular combustion reaction H + C2H4 → H2 + C2H3, using a new, high-level machine learning-based potential energy surface. In addition to the complex-mediated roaming mechanism, a non-complex forming roaming mechanism is found. It can be described as a direct inelastic collision where the departing H atom roams and then abstracts an H atom. We denoted this as “collision-induced” roaming. These two roaming mechanisms have different angular distributions; however, both produce highly internally excited C2H3. The roaming pathway leads to remarkably different dynamics as compared with the direct abstraction pathway. A clear signature of the roaming mechanism is highly internally excited C2H3, which could be observed experimentally.
Vanadium dioxide (VO2) is a multifunctional material with semiconductor-to-metal transition (SMT) property. Organic vanadium compounds are usually employed as ALD precursors to grow VO2 films. ...However, the as-deposited films are reported to have amorphous structure with no significant SMT property, therefore a postannealing process is necessary for converting the amorphous VO2 to crystalline VO2. In this study, an inorganic vanadium tetrachloride (VCl4) is used as an ALD precursor for the first time to grow VO2 films. The VO2 film is directly crystallized and grown on the substrate without any postannealing process. The VO2 film displays significant SMT behavior, which is verified by temperature-dependent Raman spectrometer and four-point-probing system. The results demonstrate that the VCl4 is suitably employed as a new ALD precursor to grow crystallized VO2 films. It can be reasonably imagined that the VCl4 can also be used to grow various directly crystallized vanadium oxides by controlling the ALD-process parameters.
Quasi-classical trajectory (QCT) calculations are performed on the molecular products CO + CH4via the tight transition state (TS) and global minimum configurations. With the aid of this theoretical ...evidence, we have re-examined the experimental results published previously to clarify the controversial issue of photodissociation dynamics of CH3CHO at 248 nm. For the CO (v = 0 and 1) bimodal rotational distributions obtained previously K.-C. Hung, P.-Y. Tsai, H.-K. Li, and K.-C. Lin, J. Chem. Phys., 2014, 140, 064313, the low-rotational (J) component is re-assigned to the contribution of triple fragmentation (H + CO + CH3), whereas the high-J component is ascribed to the CH3-roaming pathway. The H-roaming pathway is not found in the calculations. Further, the QCT results have confirmed that the CO vibrational population especially at higher states and the low-energy component of CH4 vibrational bimodality obtained experimentally are mainly produced following the TS pathway, which has never been identified before. While taking into account both the theoretical and experimental results, the ratio of the molecular products (CO(v = 1) + CH4) obtained by the triple fragmentation/roaming/TS processes is evaluated to be 0.23 : 1 : 0.29.
We present a quasiclassical trajectory study of the photodissociation of CH3CHO using a global ab initio-based potential energy surface. Calculations are performed at a total energy of 160 kcal/mol, ...corresponding to a photolysis wavelength of 230 nm, and with all trajectories initiated from the acetaldehyde global minimum. Many product channels are energetically accessible and observed at this energy, and the branching ratios to these are presented. We identify a minor channel giving H2O plus vinylidene or acetylene. Mechanisms are identified for these products, both of which originate from dissociation of vinyl alcohol an isomer of acetaldehyde. The channel CH2CHOH → HCCH + H2O produces acetylene with relatively low internal energy, while the acetylene which arises from the subsequent isomerization of vinylidene via the channel CH2CHOH → CH2C + H2O →HCCH + H2O, is highly excited. The dissociation of CD3CHO is also studied, and both HOD+DCCD (D2CC) and D2O+DCCH products are formed from the same mechanisms as in the CH3CHO dissociation.
By solving the full-dimensional time-dependent Schrödinger equation with the thermal-random-phase wavepacket method, we investigate the photoassociation (PA) process of hot (1000 K) magnesium atoms ...induced by two time-delayed femtosecond laser pulses. Driven by the 840 nm fs laser pulses, the Mg
2
molecules can be formed on the four excited states, (1)
1
Π
g
, (1)
1
Π
u
, (2)
1
Π
u
, and
(
2
)
1
Σ
u
+
, from the initial electronic ground state
X
1
Σ
g
+
. It is found that the three-photon couplings between
X
1
Σ
g
+
and the three ungerade states (1)
1
Π
u
(2)
1
Π
u
, and
(
2
)
1
Σ
u
+
, play dominant roles in the population transfer process. By scanning the pulse duration
τ
from 50 to 200 fs, and varying the delay time
δt
0
from 0 to 2
τ
fs, we find that the final PA population is strongly dependent on the two parameters. For a given
δt
0
, the parameter
τ
can induce a significant variation (2 ∼ 6.8 times) for the final PA population transfer, and for a given
τ
, one can also obtain a significant variation (2.7 ∼ 3.5 times) of the final PA population by varying
δt
0
. Additionally, the dynamics of the coherently vibrational wavepackets of the four excited states are also influenced by the two parameters.
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•Multi-transition paths are investigated for a thermal photoassociation at 1000 K.•Multi-photon coupling can form several transition paths.•The 3-photon coupling plays an important ...role.
We investigate the thermal photoassociation dynamics of the Mg atoms, from the X1Σg+ state to the (1)1Πg state, or to the other three higher excited states |i〉=(1)1Πu,(2)1Πu,(2)1Σu+. The weak two-photon coupling between X1Σg+ and (1)1Πg, the strong three-photon couplings between X1Σg+ and |i〉, and the one-photon couplings between (1)1Πg and |i〉 can form several different transition paths. We find that X1Σg+⟶+3ℏω|i〉⟶-ℏω(1)1Πg is the major path and the “V”-type Raman transition path from |i〉 to (1)1Πg takes the second place.
Graphical Abstract Display omitted
•NaI orientation up to 1000 K is simulated by full-dimensional dynamics.•A distinguishable periodic field-free orientation is observed at 1000 K.•|〈cosθ〉|max ...remains at ω0=0.15 THz with the increase in temperature.
The influence of the thermal average of initial rovibrational states on the orientation of the NaI molecule induced by a single-cycle terahertz pulse is investigated using the random-phase wavefunctions method. |〈cosθ〉|max as a function of the laser central frequency ω0 is obtained at different temperatures. Firstly, although the orientation is suppressed at high temperatures, a distinguishable periodic field-free orientation is still observable at T=1000 K. Secondly, the variation of |〈cosθ〉|max with ω0 is strongly dependent on the temperature. We ascribe this variation to different thermal distributions of the initial rovibrational states and to the consequently different final rotational distributions.
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