Kang Dai

State-resolved collisional relaxation of highly vibrationally excited CsH by CO2

Quenching of highly vibrationally excited CsH(X(1)Σ(+), v=15-23) by collisions with CO2 was investigated. A significant fraction of the initial population of highly vibrationally excited CsH(v=22) was relaxed to a low vibrational level (Δv=-5). The near-resonant 5-1 vibration-to-vibration (V-V) energy was efficiently exchanged. The rate constants for the rotational levels of CO2(00(0)0) [J=36-60] and CO2(00(0)1) [J=5-31] from the collisions with excited CsH were determined. The experiments revealed that the collisions resulting in CO2(00(0)0) were accompanied by substantial excitation in rotation and translation. The vibrationally excited CO2(00(0)1) state exhibited rotational and translational energy distributions near those of the initial state. The total quenching rates relative to the probed state of excited CsH were determined for both CO2 states. The corresponding data indicated that the gains in the rotational and translational energies in CO2 were sensitive to the collisional depletion of excited CsH.

Nascent rotational distribution for LiH(v = 0-3,J) states from collisions with H2(E = 4300 and 4800cm-1)

Rotationally state selective excitation of H2(v=1, J=1 or 3) was achieved by stimulated Raman pumping. The full state-resolved distribution of scattered LiH(v=0-3, J=0~13)molecules from collisions with excited H2(E=4300 and 4800cm-1) is reported. Nascent rotational and translational energy profiles for scattered LiH(v=0~3) molecules with J=0~13 were measured using high-resolution transient laser induced fluorescence(LIF). The product translational energy for individual J-states increases by 120% for a 13% increase in donor energy. The scattered LiH(v=0, J=0~13) molecules have a biexponential rotational distribution. Fitting the data with a two-component exponential model yields a low-energy distribution and a high-energy distribution. The rotational distribution is sensitive to donor energy. Rotational distributions of scatted LiH(v=1-3) molecules were also measured. The distribution yielded rotational temperatures at 690K for LiH/H2(E=4300cm-1) and 730K for LiH/H2(E=4800cm-1), respectively. The rate constants for appearance LiH(v=0-3,J) were determined.

Measurement of the Rb[P/(′=)−S/(=)] Effective Nonradiative Relaxation Rate near a Metallic Film

We have studied the effective nonradiative relaxation rate of the hyperfine level 87Rb[5P3/2(𝐹=3)] near a metallic film with diode laser-induced retrofluorescence spectroscopy and saturated-absorption spectroscopy technique. The glass-vapor interface is considered as two distinct regions, a wavelength-thickness vapor layer joined to the surface and a more remote vapor region. The total experimental retrofluorescence signal 𝑆ob(𝜈𝐿) is the summation of the signal originating from the far-field region 𝑆𝑇(𝜈𝐿) and the signal originating from the near-field region 𝑠𝑛(𝜈𝐿). Considering the thermalization of 87Rb(5P3/2) atoms in the far-field region, we can approximate 𝑆𝑇(𝜈𝐿) by using the vertical fluorescence signal near the entrance window. Thus we get the experimental hyperfine signal profile of 87Rb in the near-field region. The value of the effective nonradiative transfer rate 𝐴𝐹𝑛𝑓′=3→𝐹=2=2.3×108s−1 near the metallic film is relatively large compared to the spontaneous emission rate 𝐴𝐹′=3→𝐹=2=1.1×107s−1