Xuechu Li

Investigation of the 3d Rydberg state of CS2 by multiphoton ionization

Abstract Two-and three-photon resonance-enhanced multiphoton ionization spectra of the 3d Rydberg states of CS2 in the 154–160 nm region are reported. Noting that the selection rules for multiphoton transitions are quite different from those of one-photon transitions, the electronic origin of the 3dΔg Rydberg←X transition of CS2 is redefined to 63323 cm−1. The associated vibrational frequencies of the ν1, ν2 and the 2ν1, 2ν2 modes and the separation of the Π and Φ components of the ν2 vibration in this excited state are determined.

Energy transfer reactions of the He(3 2S) atom with methane and chloromethane molecules under beam conditions

Abstract Energy transfer reactions of metastable He (2 3 S) with methane and chloromethane molecules were investigated by measuring the emission spectra of the electronically excited fragments under beam conditions. The formation rate constants of the fragments CH(A 2 Δ), CH(B 2 ∑ − ), CH(C 2 ∑ + ), H * and CCl(A 2 Δ) for the reactions He(2 3 S) + CH n Cl 4- n ( n = 1−4) have been determined. The nascent rovibrational distributions of CH(A 2 Δ, v ′ = 0−2) and CH(B 2 ∑ − , v ′ = 0) have been obtained. The experimental results show that the rotational distribution of CH(A 2 Δ, v ′ = 0) from the reaction of He(2 3 S) with methane is different from that of He (2 3 S) with chloromethanes. In the former case, the rotational distribution can be expressed by a single Boltzmann temperature, while in the latter it is not a complete equilibrium distribution and may be expressed by a double Boltzmann distribution. A discussion of the reaction mechanism based on statistical theory is presented.

Vibrational population inversion in CS(A) through the dissociative excitation of CS2 by Ar(3P2)

Abstract The CS(A 1 Π → X 1 Σ + ) emission spectra resulting from the energy transfer reaction of Ar( 3 P 2 ) + CS 2 under single collision condition have been obtained. The relative vibrational populations of the nascent product CS(A 1 Π, υ′) have been determined by means of spectral simulation. A population inversion is found at υ′ = 1. The population data are approximately represented by a distribution predicted from the impulsive half collision model. The dynamics and energetics of CS(A) formation has been discussed in detail.

Rotational state-to-state energy transfer of NH2(Ã 2A1) in beam-gas condition

The detailed study on the rotational state-to-state energy transfer (RSET) of NH2(A 2A1) at a relative translational energy of about 360 cm−1 has been reported herein, by combining self-breakdown pulsed dc discharge and a photon counting technique. The transferred populations from the parent levels to the daughter levels have been obtained through the spectral simulations. It is clear that the rotational state distributions depend not only on the rotational quantum numbers of the initial and collisionally populated states, but also on the quantum number Ka. It is interesting to find that the probability of RSET behaves differently depending on the rotational quantum numbers of the parent levels, i.e., the exponential angular momentum transfer law (AMT) is preferred with the relatively low rotational levels, while the exponential energy gap law is preferred with the relatively high levels. According to the sudden approximation and the theory of Osborne et al., the experimental results are explained qualita...

Ionization process of collision of Ne(3P0,2) with CO under molecular beam condition

The ionization of CO with metastable Ne(3P0,2) in a molecular beam was studied by measuring the emission spectra of CO+ (A2II1-X2Σ+). The nascent vibrational and rotational distributions of CO+ (A) were calculated by spectral simulation and the results are discussed.

Study of the energy transfer reaction of N2(a1Πg, ν′) + CO(X1Σ, ν″ = 0) under molecular beam conditions

Abstract The energy transfer reaction of metastable N 2 ( a 1 Π g , ν′) prepared by a dc discharge of high-purity nitrogen with CO(X 1 Σ, ν″ = 0) was investigated by measuring the vacuum ultraviolet emission spectra of the electronically excited species CO(A 1 Π, ν′) and N 2 ( a 1 Π g , ν′) during the collision period under molecular beam conditions. The energy mismatch ≈ ΔE ≈ and q ν ′ ν ″ factors for both CO(A 1 Π, ν′ ← X 1 Σ, ν″) and N 2 ( a 1 Π g , ν′ → X 1 Σ, ν″) are the determining factors controlling the branching ratio from one N 2 ( a 1 Π g , ν′) donor to different vibrational levels of CO(A 1 Π, ν′) . A formula to calculate the branching ratio is presented by considering the energy mismatch ≈ ΔE ≈ and the q ν ′ ν ″ factors recalculated using a shifted value of the equilibrium internuclear distance r e of N 2 .