Vacuum Ultraviolet Photodissociation Dynamics of OCS via the F Rydberg State:theS(^(3)P_(J=2,1,0))Product Channels

Vacuum ultraviolet(VUV)photodissociation dynamics of carbonyl sulfide was investigated experimentally by using a tunable photolysis light source and the timesliced velocity map ion imaging technique.Ion images of S(^(3)P_(J=2,1,0))dissociation products were measured at five photolysis wavelengths from 133.26 nm to 139.96 nm,corresponding to the F Rydberg state of OCS.Two dissociation channels:S(^(3)P_(J))+CO(X^(1)Σ+)and S(^(3)P_(J))+CO(A^(3)Π)were observed with the former being dominant.The vibrational states of CO co-products were partially resolved in the ion images.The product total kinetic energy releases,anisotropy parameters(β),and the branching ratios of high-lying CO vibrational states were determined for the S(^(3)P_(J))+CO(X^(1)Σ^(+))channel.We found that the anisotropy parameters suddenly changed from negative to positive when OCS was excited to the higher vibrational levels of the F state.Furthermore,the anisotropy parameters for S(^(3)P_(J))products of J=2,1,0 were even different.These anomalous phenomena may result from the simultaneous existence of both parallel and perpendicular dissociation mechanisms,suggesting the involvement of other electronic states with different symmetry in the initially-excited energy region.This work provides a further understanding of the nonadiabatic couplings in the VUV photodissociation process of OCS.

Photodissociation Dynamics of OCS Near 128 nm:S(3PJ=2,1,0),S(1D2)and S(1S0)Channels

Here we report the study of the photodissociation dynamics of carbonyl sulfide in the vacuum ultraviolet region using the time-sliced velocity map ion imaging technique.Images of S(^3PJ=2,1,0),S(^1D2)and S(^1S0)products were measured at four photolysis wave-lengths of 129.32,128.14,126.99,and 126.08 nm,respectively.Four main dissociation channels:S(^3PJ=2,1,0)+CO(X^1Σ^+),S(^3PJ=2,1,0)+CO(A^3π),S(^1D2)+CO(X^1Σ^+)and S(^1S0)+CO(X^1Σ^+)channels,have been clearly observed and identified.Vibrational states of the CO co-products were partially resolved in the experimental images.From these images,the product total kinetic energy releases,the branching ratios and angular distributions of products have been derived.While the S(^3PJ=2,1,0)+CO(A^3π)product channel is formed through the adiabatic dissociation process after the excitation to the(3^1Σ^+)excited state,the results suggest that strong nonadiabatic coupling plays an important role in the formation of other three channels.

Quantum State-to-State Vacuum Ultraviolet Photodissociation Dynamics of Small Molecules

The present review focused on selected, recent experimental progress of photodissociation dynamics of small molecules covering the vacuum ultraviolet (VUV) range from 6 eV to 20 eV. These advancements come about due to the available laser based VUV light sources along with the developments of advanced experimental techniques, including the velocitymap imaging (VMI), H-atom Rydberg tagging time-of-flight (HRTOF) techniques, as well as the two-color tunable VUV-VUV laser pump-probe detection method. The applications of these experimental techniques have allowed VUV photodissociation studies of many diatomic and triatomic molecules to quantum state-to-state in detail. To highlight the recent accomplishments, we have summarized the results on several important molecular species, including H2 (D2, HD), CO, N2, NO, O2, H2O (D2O, HOD), CO2, and N2O. The detailed VUV photodissociation studies of these molecules are of astrochemical and atmospheric relevance. Since molecular photodissociation initiated by VUV excitation is complex and is often governed by multiple electronic potential energy surfaces, the unraveling of the complex dissociation dynamics requires state-to-state cross section measurements. The newly constructed Dalian Coherent Light Source (DCLS), which is capable of generating coherent VUV radiation with unprecedented brightness in the range of 50-150 nm, promises to propel the photodissociation experiment to the next level.

Wavelength Dependent Photodissociation of OCS via F 3^1ПRydberg State:CO(X1+)+S(1D2)Product Channel

The vacuum ultraviolet photodissociation of OCS via the F 3^1ΠRydberg states was investigated in the range of 134-140 nm by means of the time-sliced velocity map ion imaging technique.The images of S(^1D2)products from the CO(X^1Σ^+)+S(^1D2)dissociation channel were acquired at five photolysis wavelengths,corresponding to a series of symmetric stretching vibrational excitations in OCS(F 3^1Π,v1=0-4).The total translational energy distributions,vibrational populations and angular distributions of CO(X^1Σ^+,v)coproducts were derived.The analysis of experimental results suggests that the excited OCS molecules dissociate to CO(X^1Σ^+)and S(^1D2)products via non-adiabatic couplings between the upper F 3^1Πstates and the lower-lying states both in the C∞v and Cs symmetry.Furthermore,strong wavelength dependent behavior has been observed:the greatly distinct vibrational populations and angular distributions of CO(X^1Σ^+,v)products from the lower(v1=0-2)and higher(v1=3,4)vibrational states of the excited OCS(F 3^1Π,v1)demonstrate that very different mechanisms are involved in the dissociation processes.This study provides evidence for the possible contribution of vibronic coupling and the crucial role of vibronic coupling on the vacuum ultraviolet photodissociation dynamics.

一种可用于XeCl准分子激光传输的新型金属光波导的研究

研究了一种由表面镀铝的磷青铜作为反射面的矩形型波导传输紫外光束的性能。实验结果表明 ,这种波导能够有效地传输 30 8nm紫外光束 ,传输率可达 72 % m。充入氦气能有效地提高紫外光束的传输率。并对于不同弯曲程度对波导损耗的影响以及如何提高波导传输率 ,降低弯曲损耗进行了分析。