Direct Non-stepwise Multiple Quantum Excitations in Translation-Vibration Energy Transfer

김유항,신형규,Yoo Hang Kim,Hyung Kyu Shin Korean Chemical Society 1976 대한화학회지 Vol.20 No.2

竝進-振動에너지 變換에 있어서 中間에너지 準位를 거치지 않는 直接勵起가 多量子 振動천이에 미치는 영향을 理論的으로 조사하였다. 衝突 모형은 直線 충돌이며, 分子間의 포텐셜은 指數函數型의 것을 振動좌표(q)로 전개하고 四次項 $(q^4)$까지 包含시켜 사용하였다. $q^2$, $q^3$, $q^4$를 포함시켰을 때의 천이 확률 $(P_{m{\rightarrow}n})$에 對한 一般式을 各各 유도하고, 몇개의 충돌계에 대하여 그 값들을 계산하였다.結果를 線型化시킨 포텐셜(q)을 사용한 경우의 結果와 比較하고 直按 多量子 振動遷移가 重要한 役割을 하게 되는 條件 파라미터 ${\nalpha}$ 및 m과 관련시켜 제시하였다. Effects of direct multiple quantum excitations in vibrational energy transfer were investigated. Vibrational transition probabilities for 0${\rightarrow}$2, 0${\rightarrow}$3, and 0${\rightarrow}$4 excitations were explicitly formulated including both direct 0→n excitations and stepwise single quantum processes. For the formulation the perturbing force was derived from the exponential potential including terms up to fourth order in the vibrational amplitude. The head-on collinear collision model between a harmonic oscillator and an incident particle was employed, and the formulation was based on the semiclassical approximation. Numerical results were obtained for five different collision systems (Ar${\cdots}$O-N, He${\cdots}$H-H, He${\cdots}$H-Cl, 5${\cdots}$1-2, 2${\cdots}$12-12). Comparison between the present results and those obtained using the linearized interaction potential showed that the overall effect of including the direct multiple quantum transition is to decrease the probabilities at low collision energies and to increase them at high energies. The present results were found to be significantly different from those obtained using the linearized potential for collision systems He${\cdots}$H-H, He${\cdots}$H-Cl, and 5${\cdots}$1-2. For systems Ar${\cdots}$O-N and 2${\cdots}$12-12 the differences were negligible.

Reaction Probabilities for Three-atom Rearrangement Reaction. A + B - C = A - B + C : An Idealized Classical Approach

김유항,신형규,Kim Yoo Hang,Hyung Kyu Shin Korean Chemical Society 1975 대한화학회지 Vol.19 No.5

直線 衝突모형을 써서 三原子 置換反應 $A+B-C{\to}A-B+C$의 反應確率을 全體 에너지의 函數로 計算하였다. 使用한 포텐셜 에너지 亦是 極히 單純한 理想的인 것이다. 세原子의 質量이 모두 같은 경우에 대하여 數値로 結果를 얻어서 더욱 더 간단한 모형을 쓴 다른 硏究者들의 結果와 比較하여 定性的으로 더 나음을 알았다. An idealized linear collision model has been employed to calculate the reaction probabilities for the three-atom rearrangement reaction $A+B-C{\to}A-B+C$. Potential energy surface used is also a highly idealized one with constant values. Numerical results were obtained for the system in which the atomic masses of all three atoms are the same. Potentials were varied to see the effect of the magnitude of the opposing potential barrier on the reaction probabilities. Results obtained were compared with those obtained using different models.

Rotational State Distribution of NO after Collisions with Fast Hydrogen Atom

김유항,Kim, Yu Hang,David A. Micha Korean Chemical Society 1995 Bulletin of the Korean Chemical Society Vol.16 No.5

Based on the collisional time-correlation function approach a general analytical expression has been derived for the double differential cross-section with respect to the scattering angle and the final rotational energy, which can be applied to molecules with non-zero electronic orbital angular momentum after collision with fast hydrogen atoms. By integrating this expression another very simple expression, which gives the final rotational distribution as a function of the rotational quantum number, has also been derived. When this expression is applied to NO(2Π1/2, v'=1) and NO(2Π3/2, v'=1, 2, 3), it can reproduce the experimental rotational distribution after collision with fast H atom very well. The average rotational quantum number and average rotational energy using this expression are also in good agreement with those deduced from the experimental distributions.

Collision-induced Energy Transfer and Bond Dissociation in Toluene by H2/D2

이종백,김유항,Hyung Kyu Shin 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.12

Energy transfer and bond dissociation of C-Hmethyl and C-Hring in excited toluene in the collision with H2 and D2 have been studied by use of classical trajectory procedures at 300 K. Energy lost by the vibrationally excited toluene to the ground-state H2/D2 is not large, but the amount increases with increasing vibrational excitation from 5000 and 40,000 cm−1. The principal energy transfer pathway is vibration to translation (V-T) in both systems. The vibration to vibration (V-V) step is important in toluene + D2, but plays a minor role in toluene + H2. When the incident molecule is also vibrationally excited, toluene loses energy to D2, whereas it gains energy from H2 instead. The overall extent of energy loss is greater in toluene + D2 than that in toluene + H2. The different efficiency of the energy transfer pathways in two collisions is mainly due to the near-resonant condition between D2 and C-H vibrations. Collision-induced dissociation of C-Hmethyl and C-Hring bonds occurs when highly excited toluene (55,000-70,400 cm−1) interacts with the ground-state H2/D2. Dissociation probabilities are low (10−5~10−2) but increase exponentially with rising vibrational excitation. Intramolecular energy flow between the excited C-H bonds occurring on a subpicosecond timescale is responsible for the bond dissociation.

Reactions of Gas-Phase Atomic Hydrogen with Chemisorbed Hydrogen on a Graphite Surface

이종백,김유항,Hyung Kyu Shin 대한화학회 2007 Bulletin of the Korean Chemical Society Vol.28 No.4

The reaction of gas-phase hydrogen atoms H with H atoms chemisorbed on a graphite surface has been studied by the classical dynamics. The graphite surface is composed of the surface and 10 inner layers at various gas and surface temperatures (Tg, Ts). Three chains in the surface layer and 13 chains through the inner layers are considered to surround the adatom site. Four reaction pathways are found: H2 formation, H-H exchange, H desorption, and H adsorption. At (1500 K, 300 K), the probabilities of H2 formation and H desorption are 0.28 and 0.24, respectively, whereas those of the other two pathways are in the order of 10-2. Half the reaction energy deposits in the vibrational motion of H2, thus leading to a highly excited state. The majority of the H2 formation results from the chemisorption-type H(g)-surface interaction. Vibrational excitation is found to be strong for H2 formed on a cold surface (~10 K), exhibiting a pronounced vibrational population inversion. Over the temperature range (10-100 K, 10 K), the probabilities of H2 formation and H-H exchange vary from 0 to ~0.1, but the other two probabilities are in the order of 10-3.

Formation of Complex XeHCl+ in the Xe+ + HCl Collision

이종백,김유항,Hyung Kyu Shin 대한화학회 2008 Bulletin of the Korean Chemical Society Vol.29 No.4

The formation of complex XeHCl+ in the collision-induced reaction of Xe+ with HCl has been studied by use of classical dynamics procedures using the London-Eyring-Polanyi-Sato empirical potential energy surfaces. A small fraction of trajectories on the Xe+ + HCl and Xe + HCl+ surfaces lead to the formation of complex XeHCl+ with life-times of 1-2 ps which is long enough to survive many rotations before redissociating back to the reactant state. The formation of complex XeHCl+ occurs mainly from collision angle of Θ = 45˚.

Fragmentation Kinetics of Icosahedral Clusters: Ar12(Ar) and Ar12(Ar+)

이종백,김유항,신형규 대한화학회 2015 Bulletin of the Korean Chemical Society Vol.36 No.2

We study the fragmentation kinetics of icosahedral Ar12(Ar) and Ar12(Ar+) clusters in the temperature range 10–300 K, using a classical dynamics method for detailed forms of host–host and host–guest interaction energies composed of short- and long-range terms. The fragmentation of host atoms in charged clusters is ~20% and weakly dependent on temperature, whereas that of neutral clusters is less efficient but shows moderate temperature dependence. The dominant products from Ar12(Ar+) are 10-Ar and 9-Ar clusters, but a wider size distribution is found for Ar12(Ar) with the principal products 11- and 10-Ar clusters. The fragmentation of Ar12(Ar+) occurs on two timescales; rapid fragmentation at short time with rate coefficients ~3 × 1011/s, and slow process at long time with ~2 × 1010/s. In neutral clusters, the extent of fragmentation is low during the early period with rate coefficients ~5 × 109/s. The fragmentation dynamics is distinctly different from Ar12(Ar+), which is attributed to an escaping host atom promoting the dissociation of neighbors, a host–host cooperative effect leading to a sigmoidal rise of fragmentation. The effect is present in the temperature range 100–300 K. Fragmentation kinetics of neutral clusters is discussed in detail.

Effect of the Inner-Zone Vibrations on the Dynamics of Collision-Induced Intramolecular Energy Flow in Highly Excited Toluene

이종백,김유항,Hyung Kyu Shin 대한화학회 2005 Bulletin of the Korean Chemical Society Vol.26 No.8

Vibrational Energy Transfer in a Water Chain

이종백,김유항,Hyung Kyu Shin 대한화학회 2020 Bulletin of the Korean Chemical Society Vol.41 No.1

Vibrational energy transfer through hydrogen bonding in water chains is a fast and efficient process. The chain consisting of 10 water molecules and a ground-state nitric oxide at the end is collisionally excited by another nitric oxide molecule with an excess vibrational energy corresponding to in the v = 1 state from the other end, where the energy transfer proceeds through the hydrogen bonds. Energy transfer from the impact site to the end of chain occurs in a picosecond time scale, taking a subpicosecond over single hydrogen bond. The energy transfer pathway is a sequence of the initial OH-stretching excitation on the impact to the OH bending overtone mode and then to the bound nitric oxide through a series of low-frequency intermolecular vibrational states. More than 80% of the initial OH-stretching excitation passes through the hydrogen bonds and deposits in the bound nitric oxide at the end of the chain. In the majority of trajectories, energy passing through the N?H bond at the terminal site leads to its subsequent bond rupture, thus producing a vibrationally excited nitric oxide in the region remote from the initial impact site.

Dynamics of the Water Dimer + Nitric Oxide Collision

이종백,김유항,신형규 대한화학회 2017 Bulletin of the Korean Chemical Society Vol.38 No.2

Collision-induced intermolecular energy transfer and intramolecular vibrational redistribution in the collision of a water dimer and nitric oxide are studied by use of quasiclassical procedures. Intermolecular energy flow is shown to occur mainly through a direct-mode mechanism transferring relatively large amounts in strong collisions. About a quarter of the energy initially deposited in the dimer transfers to the ground state NO, while the rest redistributes among internal motions of the collision system. The main portion of initial energy deposited in the dimer redistributes in the stretches of the donor monomer through the 1:1 resonance followed by in the bend through the 1:2 resonance. Energy transfer from the excited NO to the ground-state dimer is equally efficient, transferring more than half the initial excitation to the donor monomer, the efficiency that is attributed to the internal modes operating as energy reservoirs. The hydrogen bond shares about 15% of the initial excitation stored in both dimer-to-NO and NO-to-dimer processes as a result of strong coupling of the hydrogen bond with the proton-donor OH bond of the monomer. A small fraction of collisions proceeds through a complex-mode mechanism and lead to NO dissociation, the dissociated O atom showing a propensity to form a new hydrogen bond.