IR chemiluminescence probe of the vibrational energy distribution of CO2 formed during steady-state CO oxidation on Pt(111) and Pt(110) surfaces

The infrared (IR) chemiluminescence spectra of CO2 were measured during the steady-state CO + O2 reaction over Pt(110) and Pt(111) surfaces. Analysis of the IR emission spectra indicates that the bending vibrational temperature (TVB), as well as the antisymmetric vibrational temperature (TVAS), was higher on Pt(110) than on Pt(111). On the Pt(110) surface, the highly excited bending vibrational mode compared to the antisymmetric vibrational mode was observed under reaction conditions at low CO coverage (theta(CO) < 0.2) or at high surface temperatures (TS > or = 700 K). This can be related to the activated complex of CO2 formation in a more bent form on the inclined (111) terraces of the Pt(110)(1 x 2) structure. On the other hand, at high CO coverage (theta(CO) > 0.2) or at low surface temperatures (TS < 650 K), TVAS was higher than TVB, which can be caused by the reconstruction of the Pt(110)(1 x 2) surface to the (1 x 1) form with high CO coverage.     

Detection of CN radicals in DC nitrogen plasma used for deposition of CNx layers

Emission spectra from a DC plasma discharge of nitrogen with a graphite cathode used for deposition of CNx layers were investigated in the visible range 350-900 nm. The spectra recorded at low and high resolution from both the negative glow and the positive column of the discharge were studied separately. All spectra are dominated by neutral and ionised N2 emission. In the positive column the violet band of the cyanogen (CN) radical was identified and analysed for vibrational structure. From a computer simulation of the rotationally resolved violet band, vibrational temperatures were derived and found to be in the intensity distribution for the nu = 0, 1 and 2 levels from thermal equilibrium. In the negative glow the strong N2+ features completely mask the spectral region of the violet band of CN. Conclusions were drawn concerning the CN formation by chemical sputtering, and the role of CN radicals in the formation of polymeric CNx layers of 1:1 = C:N stoichiometry.     

Single site electronic spectroscopy of palladium chlorin in n-octane matrixes at 7K

The high resolution, single site emission and absorption spectra of palladium chlorin (PdC) in n-octane matrixes at 7K are reported. The emission and Q and Soret band absorption regions were investigated. The vibrational frequencies of the ground and the lowest energy pipi* excited states were determined from luminescence and excitation spectra, respectively. The emission from PdC was entirely phosphorescence. The emission and Qy region spectra of the complex are similar, having intense, narrow origin bands followed by relatively weak but orderly vibrational structure. The Qx region of this metal chlorin does not have a clear origin and exhibits complex vibrational structure which increases in intensity going to higher energy. In the Soret region of PdC there is only a single intense, broad band.     

Single site electronic spectroscopy of magnesium isobacteriochlorin in n-octane matrixes at 7 K

The high resolution, single site emission and absorption spectra of magnesium isobacteriochlorin (MgiBC) in n-octane matrixes at 7 K are reported. Its emission and Q and Soret band absorption regions have been investigated. The vibrational frequencies of the ground and the lowest energy pipi* singlet excited states were determined from luminescence and excitation spectra, respectively. The emission from MgiBC at 7 K seems to be entirely fluorescence. The luminescence and Q(y) region spectra of the complex are similar, having intense, narrow origin bands followed by relatively weak, but orderly vibrational structure. The Q(x) region does not have a clear origin and exhibits complex vibrational structure that increases in intensity going to higher energy. In the Soret region the individual pipi* origins are clearly identifiable and some vibrational structure was also observed.     

Luminescence properties of uranium-activated lanthanum halotungstate (La3WO6Cl3U)

The luminescence properties of La₃W_1?xU_xO₆Cl₃ (x ≤ 0.01) are reported. The orange emission is due to a trigonal uranate prism and shows high quantum efficiency. Excitation of the host lattice does not result in uranate emission. The spectra show vibrational structure at low temperatures. An analysis of this structure has been made. For that purpose the vibrational spectra of unactivated La₃WO₆Cl₃ were studied also. The decay time of the uranate emission is one of the shortest ever observed. This is primarily due to the absence of an inversion center in the trigonal prism.     

Structure of activated complex of CO2 formation in a CO + O2 reaction on Pd(110) and Pd(111)

Examinations of CO2 formed during steady-state CO oxidation reactions were performed using infrared (IR) chemiluminescence. The CO2 was formed using a molecular-beam method over Pd(110) and Pd(111). The CO2 formation rate is temperature dependent under various partial pressure conditions. The temperature of the maximum formation rate is denoted as TSmax. Analyses of IR emission spectra at surface temperatures higher than TSmax showed that the average vibrational temperature (TVAV) is higher for Pd(111) than for Pd(110). The antisymmetric vibrational temperature (TVAS) is almost equal on both surfaces. These results suggest that the activated CO2 complex is more bent on Pd(111) and straighter on Pd(110). Furthermore, the difference in the TVAV value was small for surface temperatures less than TSmax. The TVAS value was much higher than TVAV on both surfaces. These phenomena were observed only when the surface temperature was lower than TSmax: they became more pronounced at lower temperatures, suggesting that the activated complex of CO2 formation is much straighter on both Pd surfaces than that observed at higher surface temperatures. Combined with kinetic results, the higher CO coverage at the lower surface temperatures is inferred to be related to the linear activated complex of CO2 formation.     

Single-site absorption spectroscopy of pheophytin-a and chlorophyll-a in a n-octane matrix

Site-selection experiments have been performed on pheophytin-a and chlorophyll-a in n-octane at 4.2 K. Single-site absorption spectra of both compounds were recorded, but single-site emission spectra could not be obtained. The absorption spectra show sharp lines and vibrational frequencies of the lowest excited singlet state correspond with resonance Raman frequencies. A remarkable feature of the emission is the presence of a strong 0-0 transition but extremely weak vibronic transitions.     

Emission spectra of the radical cations of hexa-, penta-, tetra-, and tri-fluorobenzenes

Emission spectra of the radical cations of the title fluorobenzenes were excited in the gaseous phase by electron impact. The spectra, vibrational fine structure discernible and the threshold energy of the emission are discussed in relation to the photoelectron spectra of the fluorobenzenes.     

Evolution of Laser Plume upon Graphite Ablation in Vacuum and Nitrogen

The propagation of carbon laser plasma during its expansion in vacuum and in a nitrogen atmosphere was studied with the use of an Nd : YAG laser (λ = 532 nm, τ = 15 ns). The presence of C₂, C₃, and CN molecules was detected in emission spectra, and the space and time characteristics of their propagation were determined. The vibrational temperatures of C₂ and CN molecules were calculated.     

傅里哀变换红外发射光谱法研究金属氧化物催化剂 I. 实验建立及氧化钼的还原-氧化研究

本文报导了傅里哀变换红外发射光谱法研究多相氧化物催化剂的实验装置的建立及实验条件的考察。设计加工了一个温度范围宽, 可在各种气氛和真空条件下原位研究氧化物催化剂的红外发射池。以MoO_3为例, 考察了样品厚度, 测试温度对发射光谱的影响。当样品量小于1 mm·cm~(-2)时, 随样品量增加, 谱峰强度线性增加, 但峰形不发生变化。当样品量高于1 mg·cm~(-2)时, 随样品量增加, 谱图严重畸变。随样品温度升高,谱峰强度近似线性增加。并用该方法研究了MoO_3在还原和再氧化过程中表面氧物种的变化。结果表明桥式MO—O—Mo物种比端基Mo=O物种较易还原, 再氧化时, Mo=O物种比Mo—O—Mo物种优先形成。     

Unit cell group analysis of rare earth elpasolites

Vibrational frequencies of rare earth elpasolites, with general formula M₂ALnX₆ (M=Cs, Rb; A=K, Na, Li; Ln=lanthanide element or yttrium; X=I, Br, Cl, F) have been determined from Raman spectroscopy and electronic absorption and emission spectra, at temperatures down to 10 K. A compilation has been made together with available literature data. The 10 unit cell group vibrational frequencies have been satisfactorily fitted by using a modified valence force field. The trends in the derived force constants are reasonable from a physical viewpoint.     

Time‐Resolved FTIR Emission Spectroscopy of Transient Radicals

Fourier Transform spectroscopy with 10^?8 second time resolution for recording IR emission spectra has been developed as an efficient means for detecting previously unknown vibrational modes of transient radicals. 193 nm photodissociation of a precursor molecule is used to generate vibrationally excited radicals, from which IR emission is recorded with time and spectral resolution. Assignment of the spectra is performed using information obtained through multiple precursors, isotopic substitution, time dependence of emission intensity, theoretical calculations, and 2‐dimensional cross‐spectra correlation analysis. The radicals vinyl, cyanovinyl, and OCCN have been studied with many vibrational modes identified.     

Raman spectra from ethylene and deuterated ethylene chemisorbed on a silica-supported nickel catalyst

The Raman spectra of ethylene and deuterated ethylene chemisorbed on silica-supported nickel have been measured in the frequency range 50–3400 cm^?1. At room temperature, a Raman spectrum is observed which corresponds to ethylene chemisorbed under dehydrogenation and it is rather similar to the spectrum of chemisorbed acetylene. For a comparison therefore, the Raman spectra of acetylene and deuterated acetylene were also measured. In addition, the vibrational spectrum of chemisorbed benzene was recorded. At temperatures T ? 200 K, ethylene is found to be associatively chemisorbed without dehydrogenation.The vibrations observed are described in the approximation of a surface molecule with covalent bonding to two or three surface nickel atoms. The symmetry seems to be slightly distorted C_2v or C_s. The vibrational spectrum is discussed with respect to a metal- surface selection rule. In order to improve the reliability of the assignments for localized vibrational modes, a normal coordinate analysis and a force constant calculation have been done for chemisorbed acetylene.     

State dynamics of acetylene excited to individual rotational level of the V1(2)K1(0,1,2) subbands

The dynamics of the IR emission induced by excitation of the acetylene molecule at the 3(2) Ka2, A1Au<--4(1) la1, X1Sigmag+ transition was investigated. Vibrationally resolved IR emission spectra were recorded at different delay times after the laser excitation pulse. The observed IR emission was assigned to transitions between vibrational levels of the acetylene molecule in the ground state. Values of the relaxation parameters of different vibrational levels of the ground state were obtained. The Ti-->Tj transition was detected by cavity ring-down spectroscopy in the 455 nm spectral range after excitation of the acetylene molecule at the same transition. Rotationally resolved spectra of the respective transition were obtained and analyzed at different delay times after the laser excitation pulse. The dynamics of the S1-->Tx-->T1-->S0 transitions was investigated, and the relaxation parameter values were estimated for the T1 state.     

O(3P)原子与CS2反应可见化学发光研究

在交叉分子束装置上研究了基态氧原子O(3P)与二硫化碳反应的可见光区(380～500 nm)化学发光，得到的光谱标识为SO2分子 3B1→ 1A1自旋禁阻跃迁发射谱，实验中得到的上态主要是振动基态和弯曲模ν2激发的振动激发态，通过对不同压力情况下光谱的分析和反应通道的讨论，确认 3B1态的SO2来自于反应的多级过程.     

Rydberg fingerprint spectroscopy of hot molecules: structural dispersion in flexible hydrocarbons

We explore how structural dispersion in flexible hydrocarbon chain molecules at very high temperatures is reflected in the photoionization spectra of Rydberg levels. The spectra of N,N-dimethylisopropanamine, N,N-dimethyl-1-butanamine, N,N-dimethyl-2-butanamine, N,N-dimethyl-3-hexanamine, and 1,4-dimethylpiperazine, taken at effective vibrational temperatures of 700-1000 K, show well-resolved features stemming from the 3p and 3s Rydberg states. The line shapes observed in molecules with internal rotation degrees of freedom show that multiple structures are populated. Following up on the discovery that low-lying Rydberg states provide sensitive fingerprints of molecular structures, this work supports Rydberg fingerprint spectroscopy as a tool to probe structural details of molecules in the presence of complex energy landscapes and at high vibrational temperatures. A simple model accounts for the sensitivity of Rydberg fingerprint spectroscopy to the molecular shape, as well as the relative insensitivity of the spectra toward vibrational excitation.     

Diagnostics and Application of the High Frequency Plasma Pencil

The so called high frequency plasma pencil is a source of highly active environment (electrons, ions, reactive radicals, excited atoms, and molecules) which can be generated at atmospheric, reduced or increased pressure, preserving a good control of the performance. The discharge can be either unipolar or bipolar. The properties of unipolar atmospheric pressure discharges are discussed on the basis of simple theoretical considerations and electric probe measurements. The plasma pencil discharge is studied by optical emission spectroscopy in the gas phase at atmospheric pressure as well as immersed in liquid using argon as a working gas. From the emission spectra the electron, vibrational and rotational temperatures are calculated for various distances from the plasma pencil electrode. Several technological applications like restoration of archaeological glass and metal artifacts, fragmentation of molecules for microelectrophoresis and plasma polymerization are summarized. An advantage of the plasma pencil is that it can be easily operated and controlled.     

时间分辨傅立叶变换红外发射光谱技术研究叔丁基亚硝酸酯的光解动力学

利用时间分辨傅立叶变换红外(TR-FTIR)发射光谱技术对叔丁基亚硝酸酯355 nm激光光解动力学进行研究. 通过对实验观测到的光解产物NO的时间分辨红外发射谱进行分析, 获得了NO的转动温度和相对振动布居, 并发现了振动布居的反转现象. 结合前人的工作, 我们确认了光解产物NO的最大振动布居量子数υ与光解光激发的母体分子N=O伸缩振动的泛频跃迁所涉及的振动量子数υ*之间的关系为υ=υ*-1.     

Influences of Quantum Mechanically Mixed Electronic and Vibrational Pigment States in 2D Electronic Spectra of Photosynthetic Systems: Strong Electronic Coupling Cases

In 2D electronic spectroscopy studies, long‐lived quantum beats have recently been observed in photosynthetic systems, and several theoretical studies have suggested that the beats are produced by quantum mechanically mixed electronic and vibrational states. Concerning the electronic‐vibrational quantum mixtures, the impact of protein‐induced fluctuations was examined by calculating the 2D electronic spectra of a weakly coupled dimer with the Franck‐Condon active vibrational modes in the resonant condition [Fujihashi et al., J. Chem. Phys.­ 2015 , 142, 212403.]. This analysis demonstrated that quantum mixtures of the vibronic resonance are rather robust under the influence of the fluctuations at cryogenic temperatures, whereas the mixtures are eradicated by the fluctuations at physiological temperatures. However, this conclusion cannot be generalized because the magnitude of the coupling inducing the quantum mixtures is proportional to the inter‐pigment electronic coupling. In this study, we explore the impact of the fluctuations on electronic‐vibrational quantum mixtures in a strongly coupled dimer with an off‐resonant vibrational mode. Toward this end, we calculate energy transfer dynamics and 2D electronic spectra of a model dimer that corresponds to the most strongly coupled bacteriochlorophyll molecules in the Fenna‐Matthews‐Olson complex in a numerically accurate manner. The quantum mixtures are found to be robust under the exposure of protein‐induced fluctuations at cryogenic temperatures, irrespective of the resonance. At 300 K, however, the quantum mixing is disturbed more strongly by the fluctuations, and therefore, the beats in the 2D spectra become obscure even in a strongly coupled dimer with a resonant vibrational mode. Further, the overall behaviors of the energy transfer dynamics are demonstrated to be dominated by the environment and coupling between the 0 0 vibronic transitions as long as the Huang‐Rhys factor of the vibrational mode is small. The electronic‐vibrational quantum mixtures do not necessarily play a significant role in electronic energy transfer dynamics despite contributing to the enhancement of long‐lived quantum beating in the 2D spectra.