Non-collinear optical parametric chirped-pulse amplifier for few-cycle pulses

Modified parametric coupled equations for three-wave interaction in non-collinear optical parametric chirped-pulse amplification (OPCPA) are presented, in which the effects from the non-collinear configuration have been taken into account. By utilizing this new model, a two-stage OPCPA system based on a BBO crystal is numerically calculated with a split-step Fourier transform algorithm. Tracing the dynamics of the signal wave in the crystal reveals that in the first stage spectral gain narrowing occurs due to the weak input signal intensity and the non-uniform temporal distribution of the pump light. However, in the saturation regime the spectrum of the signal will be broadened as a consequence of back conversion. The simulation shows that it is crucial to correctly control the experimental parameters to balance both processes. For maximizing the energy-bandwidth product (EBP), an optimized configuration is sought by examining several parameters such as pump intensity, seed energy and crystal length. With a pump intensity of 7.75 GW/cm² and a crystal length between 3.75 and 4.25 mm pulses with a sub-10 fs duration can be amplified with a total gain of up to 1.7×10⁶.     

NO分子和氧原子的高分辨离子谱实验研究

共振增强多光子电离及飞行时间质谱技术是一种具有高分辨率、高灵敏度的光谱研究技术。利用上述技术研究了由激光光解NO2产物-NO与原子O的离子谱,获得了振转态高度分辨的NO(X^2П,v″,J″)γ(0,0)γ(0,1)γ(1,1)带的离子谱以及自旋-轨道精细能级分辨的氧原子O(2P^3PJ^″=2,1,0)离子谱。氧原子O(2P^3PJ^″=2→3P^3PJ^″、2P^3PJ^″=1→3P^3PJ′、2P^3PJ″=0→3P^3PJ′)的离子信号位于紫外电离探测激光的波长分别为225．65nm,226．04nm,226．23nm。实验表明,共振增强多光子电离加飞行时间技术研究原子、分子光谱其灵敏度与分辨率远高于常用的激光感生荧光方法。所得到的NO分子与氧原子的离子谱及它们的离子信号对NO2分子光解及NO分子与氧原子的电离动力学研究提供了有益的实验信息。     

Cover Picture: Photoprogrammable Organic Light‐Emitting Diodes (Angew. Chem. Int. Ed. 22/2009)

Programmable organic light‐emitting diodes: UV irradiation converts an oxetane‐functionalized dithienylethene derivative from its colorless open form into a dark blue closed form, while visible light reverses the reaction. In the Communication on page 4038 ff., K. Meerholz and co‐workers describe a reversibly switchable organic light‐emitting diode based on this principle.

     

Afzeliixanthones A and B, two new prenylated xanthones from Garcinia afzelii ENGL. (Guttiferae)

Two new prenylated xanthones, afzeliixanthones A (1) and B (2), together with three known xanthones (3-5) and two phytosterols, beta-sitosterol and stigmasterol, were isolated from the CH2Cl2/MeOH (1:1) extract of the stem bark of Garcinia afzelii ENGL. collected in the South West Province of Cameroon. Structures were mainly established using one and two-dimensional NMR and mass spectroscopies. The antioxidant activities of the crude extracts as well as the new compounds (1) and (2) were evaluated.     

Visualization of high-order dispersion for compression of few-cycle pulses

We present a visually intuitive method for higher-order dispersion compensation based on multi-photon interpulse interference pulse scans. The dispersion values obtained from these scans are fed back as a correction to an acousto-optical programmable dispersive filter to compensate residual higher-order dispersions up to fifth order. This method is applied to the dispersion management of a non-collinear optical parametric chirped-pulse amplifier. A grism-pair stretcher is designed based on a global dispersion balance which provides a large stretching factor and supports a spectral bandwidth of up to 320 nm. It is implemented in a two-stage three-pass non-collinear optical parametric chirped-pulse amplifier and stretches 6-fs seed pulses to about 80 ps from 700 to 1,000 nm. The amplified pulses are compressed by material dispersion. Pulses of less than 10-fs duration with a pulse energy of 125 μJ are obtained at 20-kHz repetition rate.     

激光光解NO2产物--氧原子O(3PJ″)的REMPI离子谱

由 Nd:YAG激光器三倍频 ,输出波长为λ =355 nm( 28 169 cm- 1)的激光光解 NO2分子产生的氧原子 ,通过共振增强多光子电离( REMPI resonance enhanced multiphoto ionization)及飞行时间( TOF time of flight)质谱技术 ,获得了自旋轨道精细能级分辨的氧原子 O(2p 3PJ″ =2,1,0)离子谱 .氧离子信号强度与 UV电离激光能量(λ≈ 226 nm)之间的关系能用三次方曲线很好拟合 ,它表明光解产物氧原子是通过( 2+ 1)多光子吸收过程而被电离的 .由离子信号得到的氧原子基态三个自旋轨道支能级布居比 f1=I(3P1)/I(3P2)与 f0=I(3P0)/I(3P2)分别为 0.54± 0.09和 0.20± 0.04,并且在不同的光解激光能量下其布居比保持不变 .这一比值与统计分布计算的值为 0.6和 0.2一致(即统计分布 3P2∶ 3P1∶ 3P0=1:0.6:0.2) .这是由于样品 (NO2)在较低的压力下( 1.33× 10- 4 Pa)和极短的光解电离时间范围内( 10- 8 s) ,产物 O( 3PJ″)支能级间几乎不可能发生碰撞能量转移 ,因此 ,氧原子三个自旋轨道角动量分裂能级布居 O( 3PJ″ =2,1,0)是统计分布的.     

激光光解NO_2产物——氧原子O(~3P_(J''''''''))的REMPI离子谱

由Nd:YAG激光器三倍频,输出波长为λ=355 nm(28 169 cm~(-1))的激光光解NO_2分子产生的氧原子,通过共振增强多光子电离(REMPI resonance enhanced multiphoto ionization)及飞行时间(TOF time of flight)质谱技术,获得了自旋-轨道精细能级分辨的氧原子O(2 p~3P_J~″=2,1,0)离子谱.氧离子信号强度与UV电离激光能量(λ≈226 nm)之间的关系能用三次方曲线很好拟合,它表明光解产物氧原子是通过(2+1)多光子吸收过程而被电离的.由离子信号得到的氧原子基态三个自旋-轨道支能级布居比f_1=I(~3P_1)/I(~3P_2)与fo=I(~3P_0)/I(~3P_2)分别为0.54±0.09和0.20±0.04,并且在不同的光解激光能量下其布居比保持不变.这一比值与统计分布计算的值为0.6和0.2一致(即统计分布~3P_2:~3P_1:~3P_0=1:0.6:0.2).这是由于样品(NO_2)在较低的压力下(1.33×10~(-4)Pa)和极短的光解-电离时间范围内(10~(-8)s),产物O(~3P_J~″)支能级间几乎不可能发生碰撞能量转移,因此,氧原子三个自旋-轨道角动量分裂能级布居O(~3P_J~″=2,1,0)是统计分布的.     

Identification of Cu(II)/Cu(III) couples in binuclear copper(II) complexes

A new series of binuclear copper(II) complexes were synthesised and studied by magnetic, spectral, ESR and cyclic voltammetry methods. The μ_eff values per copper atom correspond to the values observed for mononuclear copper(II) complexes. ESR spectral data in solution indicate weak interactions resulting from the electron delocalisation through the ligand system. Two nearly reversible red-ox couples are identified at $\text{+}\text{?}$0.50 V and $\text{+}\text{?}$0.75 V vs SCE. They correspond to Cu(II)αCu(III) red-ox processes, successively occurring at the two copper sites in the binuclear complexes.