Zhang Wen-jun, Feng Li, Li Jia-ling, Liu Jing, Dai Kang, Shen Yi-fan
Guang Pu Xue Yu Guang Pu Fen Xi. 2014 Jun;34(6):1492-6.
Energy transfer in H2 (1,1) +CO2 collisions was investigated using high resolution transient laser spectroscopy. Rotational state selective excitation of v = 1 for rotational level J = 1 was achieved by stimulated Raman pumping. Energy gain into CO2 resulting from collisions with H2 (1,1) was probed using transient absorption techniques, Distributions of nascent CO2 rotational populations in both the ground (00 degrees 0) state and the vibrationally excited (00 degrees 1) state were determined from overtone absorption measurements. Translational energy distributions of the recoiling CO2 in individual rovibrational states were determined through measurement of Doppler-broadened transient line shapes. A kinetic model was developed to describe rates for appearance of CO2 states resulting from collisions with H2(1,1). From scanned CARS (coherent anti-stokes Raman scattering) the spectral peaks population ratio n0/n1 was obtained, where n0 and n1 represent the number densities of H2 at the levels (0,1) and (1,1), respectively. Using rotational Boltzmann distribution of H2 (v = 0) at 300 K, n1 was yielded. Values for rate coefficients were obtained using data for CO2 (00 degrees 0) J = 48 to 76 and CO2 (00 degrees 1) J = 5 to 33. The rate coefficients derived from appearance of the (00 degrees 0) state have values of K(tr) = (3.9 ± 0.8) x 10(-11) cm3 x molecule(-1) x s(-1) for J = 48 and k(tr) = (1.4 ± 0.3) x 10(-10) cm3 x molecule(-1) x s(-1) for J = 76, with a monotonic increase for the higher J states. For the (00 degrees 1) state, values of k(tr) remain fairly constant at k(tr) = (4.3 ± 0.9) x 10(-12) cm3 x molecule(-1) x s(-1). Rotational populations for the nascent CO2 states were measured at 0. 5 μs following excitation of H2. The transient population for each state was fit using a Boltzmann rotational distribution. The CO2 (00 degrees 0) J = 48-76 rotational states were populated substantially relative to the initial 300 K CO2 distributions, and the distribution is described by Trot. The excited (00 degrees 1) state has T(rot), 310 K. The center-of-mass translational temperatures for the (00 degrees 0) state are all much greater than 300 K, with T(rel) = 1 532 K for J = 76. In contrast, transient line profiles for the J = 5 - 33 levels of excited (00 degrees 1) state do not show any broadening above the initial 300 K distributions, indicating that excitation to the (00 degrees 1) state is not accompanied by translational energy change.
利用高分辨率瞬态激光光谱研究了H₂(1,1)+CO₂碰撞中的能量转移。通过受激拉曼泵浦实现了对转动能级J = 1的v = 1转动态的选择性激发。利用瞬态吸收技术探测了与H₂(1,1)碰撞导致的CO₂的能量增益，通过泛音吸收测量确定了基态(00⁰0)和振动激发态(00⁰1)中新生CO₂转动布居的分布。通过测量多普勒展宽的瞬态线形确定了各个振转态中反冲CO₂的平动能分布。建立了一个动力学模型来描述与H₂(1,1)碰撞导致的CO₂态出现的速率。从扫描的相干反斯托克斯拉曼散射（CARS）中获得了光谱峰布居比n₀/n₁，其中n₀和n₁分别表示H₂在(0,1)和(1,1)能级的数密度。利用300K时H₂(v = 0)的转动玻尔兹曼分布，得出了n₁。使用CO₂(00⁰0) J = 48至76和CO₂(00⁰1) J = 5至33的数据获得了速率系数值。从(00⁰0)态出现推导的速率系数对于J = 48有K(tr) = (3.9±0.8)×10⁻¹¹cm³·分子⁻¹·s⁻¹，对于J = 76有k(tr) = (1.4±0.3)×10⁻¹⁰cm³·分子⁻¹·s⁻¹，对于较高J态呈单调增加。对于(00⁰1)态，k(tr)值相当恒定，为k(tr) = (4.3±0.9)×10⁻¹²cm³·分子⁻¹·s⁻¹。在H₂激发后0.5μs测量了新生CO₂态的转动布居。每个态的瞬态布居用玻尔兹曼转动分布进行拟合。相对于初始300K的CO₂分布，CO₂(00⁰0) J = 48 - 76转动态大量布居，该分布由Trot描述。激发态(00⁰1)的T(rot)为310K。(00⁰0)态的质心平动温度都远高于300K，对于J = 76，T(rel) = 1532K。相比之下，激发态(00⁰1)的J = 5 - 33能级的瞬态线形在初始300K分布之上没有显示出任何展宽，表明激发到(00⁰1)态不伴随平动能变化。
