Rotational and vibrational state distributions of NaH in the reactions of Na(4S2,3D2,and6S2) with H2: Insertion versus harpoon-type mechanisms

Abstract

By using a pump-probe technique, the nascent rotational and vibrational state distributions of NaH are obtained in the Na(4 (2)S,3 (2)D, and 6 (2)S) plus H(2) reactions. The rotational distributions for the Na(4 (2)S,3 (2)D) reactions yield a bimodal feature with a major component peaking at J=20-22, similar to that obtained previously in the 4 (2)P reaction, whereas the Na(6 (2)S) reaction gives rise to a distinct distribution with a much lower rotational temperature. The vibrational populations (v=0-4) for these 4 (2)S, 3 (2)D, and 6 (2)S reactions are characterized by corresponding temperatures of 1692+/-120, 819+/-35, and 5329+/-350 K. Due to a significant contribution of configurational mixing between different states with the same symmetry, the collision species initiated from the 4 (2)S and 3 (2)D states are anticipated to track along the entrance surface in a near C(2v) symmetry, then undergo nonadiabatic transition to the inner limb of the reactive 2A(') surface. In contrast, the reaction pathway for the Na(6 (2)S) state with a significantly reduced ionization energy is anticipated to follow a harpoon-type mechanism via a (near) collinear configuration. The increased atomic size of Na may hinder the insertion approach.

Non-adiabatic quantum dynamical studies of Na ( 3 p ) + HD ( ν = 1 , j = 0 ) → NaH / NaD + D / H reaction*

“…The reactions of excited-state alkali atoms with hydrogen molecule have received much attention because of their unique advantages for studying non-adiabatic processes in reaction dynamics. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] As the most intriguing characteristic, the alkali-hydrogen reactions are highly endoergic in their ground state. The energy to initiate the reaction is easily achieved via electronic excitation of the alkali atom, therefore the transitions of electronic states necessarily occur when the reaction proceeds from the excited entrance valley to the ground exit valley.…”

New diabatic potential energy surfaces of the NaH2 system and dynamics studies for the Na(3p) + H2 → NaH + H reaction

“…The NaH 2 presents a simple prototype of such collision systems, and numerous experimental results 15–22 about the collisions between excited sodium atom and hydrogen molecule are available. Botschwina et al .…”

“…This experiment showed the formation of NaH via the Na(3p) + H 2 reaction follows a two-step mechanism, which is opposite to the direct reaction of Na(4p) + H 2. In 2008, Chang and co-workers 22 studied the rotational and vibrational state distributions of NaH in the reactions of high exited states Na(4 2 S, 3 2 D and 6 2 S) with H 2 by using the pump-probe technique. The authors concluded that the Na(6 2 S) reaction has a dramatically reduced ionization energy, and the corresponding reaction pathway maybe prefer a harpoon model via a near collinear configuration.…”

Quasiclassical trajectory calculations for Li(22PJ) + H2 → LiH(X1Σ+) + H: Influence by vibrational excitation and translational energy

“…[3][4][5][6][7][8][9], Rb (Refs. [19][20][21][22] and Li (Refs. 12-18) via a collinear approach geometry.…”