Laser Spectroscopy: Basic Concepts and Instrumentation
Laser Spectroscopy: Basic Concepts and Instrumentation
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DOI：
10.1007/978-3-662-08260-7
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发表时间：
1996-03
期刊：
影响因子：
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通讯作者：
W. Demtröder
中科院分区：
文献类型：
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作者：
W. Demtröder
我们关于原子和分子结构的大部分知识都是基于光谱研究。因此，光谱学对原子和分子物理学、化学和分子生物学的现状做出了杰出的贡献。关于分子结构和分子与其周围环境相互作用的信息可以通过多种方式从电磁辐射与物质相互作用时产生的吸收或发射光谱中得出。谱线的波长测量可以确定原子或分子系统的能级。线强度与跃迁概率成正比，跃迁概率衡量分子跃迁的两个能级耦合的强度。由于跃迁概率取决于两个能级的波函数，因此强度测量可用于验证激发电子的空间电荷分布，而这只能通过薛定谔方程的近似解来粗略计算。谱线的自然线宽可以通过特殊技术来解析，从而可以确定激发分子态的平均寿命。多普勒宽度的测量得出发射或吸收分子的速度分布以及样品的温度。从谱线的压力展宽和压力偏移中，可以提取有关碰撞过程和原子间势的信息。外部磁场或电场引起的塞曼和斯塔克分裂是测量磁矩或电矩以及阐明原子或分子中不同角动量耦合的重要手段，即使是复杂的电子构型。谱线的超精细结构产生有关原子核和电子云之间相互作用的信息，并允许确定核磁偶极矩、电四极矩甚至更高的矩，例如八极矩。时间分辨测量使光谱学家能够跟踪基态和激发态分子的动力学过程，以研究碰撞过程和各种能量转移机制的细节。光学激发与飞秒到阿秒激光脉冲和同一时间尺度上的 X 射线衍射相结合，可以实现电子激发态分子结构的时间分辨快照，而不会被激发分子的振动冲掉，因为 X 射线衍射图案是在
Most of our knowledge about the structure of atoms and molecules is based on spectroscopic investigations. Thus spectroscopy has made an outstanding contribution to the present state of atomic and molecular physics, to chemistry, and to molecular biology. Information on molecular structure and on the interaction of molecules with their surroundings may be derived in various ways from the absorption or emission spectra generated when electromagnetic radiation interacts with matter. Wavelength measurements of spectral lines allow the determination of energy levels of the atomic or molecular system. The line intensity is proportional to the transition probability, which measures how strongly the two levels of a molecular transition are coupled. Since the transition probability depends on the wave functions of both levels, intensity measurements are useful to verify the spatial charge distribution of excited electrons, which can only be roughly calculated from approximate solutions of the Schrödinger equation. The natural linewidth of a spectral line may be resolved by special techniques, allowing mean lifetimes of excited molecular states to be determined. Measurements of the Doppler width yield the velocity distribution of the emitting or absorbing molecules and with it the temperature of the sample. From pressure broadening and pressure shifts of spectral lines, information about collision processes and interatomic potentials can be extracted. Zeemann and Stark splittings by external magnetic or electric fields are important means of measuring magnetic or electric moments and elucidating the coupling of the different angular momenta in atoms or molecules, even with complex electron configurations. The hyperfine structure of spectral lines yields information about the interaction between the nuclei and the electron cloud and allows nuclear magnetic dipole moments, electric quadrupole moments or even higher moments, such as octupole moments to be determined. Time-resolved measurements allow the spectroscopist to follow up dynamical processes in ground-state and excited-state molecules, to investigate details of collision processes and various energy transfer mechanisms. The combination of optical excitation with femto-to attosecond laser pulses and X-ray diffraction on the same time scale allows time-resolved snapshots of molecular structure in electronically excited states not washed out by vibrations of the excited molecule, because the X-ray diffraction pattern is measured within a