Terms related to molecular spectroscopy [和分子光譜術相關的專有名詞]

[A B C D E F G H I J K L M N O P Q R S T U V W X Y Z]

Ab initio calculation
Ab initio calculation uses the correct molecular electronic Hamiltonian (Hel) and does not introduce experimental data (other than the values of the fundamental physical constants) into calculation. For example, the Hartree-Fock self-consistent-field (SCF) molecular orbital (MO) method seeks the orbital wavefunction (phi) that minmizes the variational integral <(phi)|Hel|(phi)>, where  Hel is the true Hamiltonian. Ab inito是拉丁文,原意為from scratch”(從頭開始),從事量子計算時,除了使用基本的物理常數和薛丁格方程式(Schrödinger equation),不加入任何假設。此類量子化學計算可用於預測分子的結構 能量振動頻率等物理量和分子特性 物理化學常用套裝軟體稱為Gaussian98可向Gaussian Inc.公司(網址: http://www.gaussian.com)購買很有用的參考書: "Ab Initio Molecular Orbital Theory", W. J. Hehre, L. Radom, P. R. Schleyer, and J. A. Pople, John Wiley & Sons, Inc., New York, 1986.

Adiabatic process
從光激發與光游離角度來看,Adiabatic process是系統受外力作用的的過程中(例如當分子吸收光),系統(分子)在激發態或離子態時的能階會達到一個定值,也就是說分子最後會處於某穩定的能階狀態,通常改變過程速度較"慢",系統總能不變,但系統內的能量形態可能會相互轉移。例如光游離的過程中,若所使用的光源是奈秒的雷射,離子態的分子最後會處於某穩定的不振動態,或某種模式的振動態。相對地,non-adiabatic (或diabatic) process則是系統改變的過程,能階維持一個範圍,也就是說分子處於許多能階的集合,通常改變過程速度較快(sudden或impulse)。通常光游離的過程中,若所使用的光源是皮秒或飛秒的雷射,則涉及到non-adiabatic過程,這類實驗(例如時間解析光譜術)可用來測量分子的某些特性(例如分子在某能階狀態的壽命或衰變速率、化學鍵的斷裂、電子或質子的躍遷)如何隨時間變化。

ZEKE或MATI實驗的情況則稍有不同,首先以奈秒雷射將分子激發到高雷得堡態[能階僅低於分子真實的游離臨界幾個波數],再以脈衝場將它游離,此過程涉及到高雷得堡態分子和電場的作用,所測得精確的游離能,稱為adiabatic ionization energy

AM1, Austin method 1, a semiemprical procedure

Angular momentum
Angular momentum (角動量)是物體轉動的動量,物體角動量愈大愈難使它靜止。古典力學中,角動量為,其中I moment of inertia (慣性力距) I = mvrω則是角速度。量子力學中,角動量為{j(j+1)}1/2ħ,其中 j 必需是零或正整數。

Harmonic oscillator (簡諧振動子)的能量(potential)displacement(位移)平方成正比,anharmonic oscillaor則不。

Astronomical Spectroscopy
Energy from celestial objects is used to analyze their chemical composition, density, pressure, temperature, magnetic fields, velocity, and other characteristics. There are many energy types (spectroscopies) that may be used in astronomical spectroscopy.
Atomic Absorption Spectroscopy
Energy absorbed by the sample is used to assess its characteristics. Sometimes absorbed energy causes light to be released from the sample, which may be measured by a technique such as fluorescence spectroscopy.

Atomic units
質量以me (atomic mass) 的倍數表示。Electron rest mass, me = 9.105 x 10-31 kg

電量以e (elementary charge) 的倍數表示。Elementary charge, e = 1.602 x 10-19 C

長度以a0 (Bohr radius) 的倍數表示。Bohr, a0 = 4πε0•ħ2 / mee2 = 0.5292 Å = 5.292 x 10-11 m

Action (energy x time)ħ 的倍數表示。Planck’s constant / 2π = 1.055 x 10-34 J•s

能量以hartree的倍數表示。Eh = ħ2 / mea02 = 2hcR¥ = 4.369 x 10-18 J

Attenuated Total Reflectance Spectroscopy
This is the study of substances in thin films or on surfaces. The sample is penetrated by an energy beam one or more times and the reflected energy is analyzed. Attenuated total reflectance spectroscopy and the related technique called frustrated multiple internal reflection spectroscopy are used to analyze coatings and opaque liquids.

 Auger spectroscopy
In Auger spectroscopy a beam of high-energy radiation is used to eject an electron from a core orbital. The resulting positive ion can relax to a lower energy state by dropping a valence electron into a core hole. The energy released in this process can be (1) emitted as a quantum of X-radiation (X-ray fluorescence) or (2) used to eject a valence electron from the ion (the Auger process). The ejected electron is called “Auger electron” and possesses kinetic energy characteristic to the atom from which it is emitted. This kinetic energy is determined by the energy released in relaxation and the binding energy of the ejected electron. Hence, it is independent of the energy of the exciting beam. For this reason, the excitation source for Auger spectroscopy usually consists of a beam of electrons from a high-powered electron gun. Since the impinging electron can loose any portion of its kinetic energy to the bound electrons, the primary electrons (photoelectrons) are ejected with a random distribution of energies while the secondary electrons (Auger electrons) have discrete energies. The resulting spectrum exhibits Auger peaks superimposed on a continuous background of primary electrons; it is hence displayed as the first derivative of the actual spectrum. Auger peaks are commonly observed in ordinary X-ray electron spectroscopy.

There exist both the discrete (neutral) and continuous states above the ionization limit. When a molecule is excited to a discrete (neutral) state, radiationless transitions can take place from the discrete (neutral) state to the continuum state. Such a process is called autoionization.

Autoionization state
Autoionization states are bound states whose energy levels lie above the ionization limit. Such states usually arise when the internal shell is excited.

Born-Oppenheimer (B-O) approximation
The Born-Oppenheimer approximation is the separation of the motion of the electron in a molecule from the motion of the nuclei. It follows that the electron wavefunction can be calculated for any specific static nuclear framework. [B-O近似假設:在分子內的電子的運動不受核子的運動干擾(把核子的運動視為靜止),因此可計算出電子的波函數,即可描述電子在空間運動的軌跡。]

Boson, A boson is a particle with integral spin (including zero), e.g. 2H (I = 1), α-particle (I = 0).

Bracket notation
Paul Dirac denoted the state of the system by “ket”, |n>, corresponding to the wavefunction ψn, where stands for the quantum numbers needed to specify the state. In addition, “bra” <n| denotes complex conjugate ψn*. Thus, <n|n> = òψnψn*dτ.

The rotational transition that accompany a vibrational transition of a molecule give rise to lines in a spectrum that can be grouped into branches:

O branch: lines arising from J → J-2 (Raman spectra)

P branch: lines arising from J → J-1 (infrared and Raman spectra)

Q branch: lines arising from J → J (if allowed)

R branch: lines arising from J → J+1 (infrared and Raman spectra)

S branch: lines arising from J → J+2 (Raman spectra)

CIS, Configuration interaction singles
It is a computational procedure for obtaining optimized structure, energy, vibrational frequency, and other properties of molecules in the electronically excited state. 這是個量子化學計算步驟,用來預測分子在電子激發態時的最佳結構、能量、振動頻率等特性。

Coriolis force
FCoriolis = 2mvaωsinφ, where m is the mass of the particle, va its apparent velocity with respect to the moving coordinate system, the angular velocity of the coordinate system with respect to a fixed coordinate system, and ω the angle between the axis of rotation and the direction of va. The Coriolis occurs only for a moving particle (va ≠ 0) and is directed at right angles to the direction of motion and at right angles to the axis of rotation. Introduction of the Coriolis force leads to an additional coupling between rotation and vibration (Coriolis coupling) which is in general much larger than the effect of the centrifugal force. [FCentrifugal = mrω2, where r is the distance from the axis of rotation]

Two or more wavefunctions are degenerate if they have the same energy. [具相同能量的兩個以上的波函數稱為degenerate]

Doppler width, δω

δωD = (ω0/c){8kT•ln2/m}1/2 = (2ω0/c){2RT•ln2/M}1/2

δνD = 7.16 x 10-7ν0{T/M}1/2 [s-1]

(a)    VUV: For the Lyman α line (2P → 1S transition in H atom) in a discharge with
temperature T = 1000 K, M = 1, λ = 1216 Å, ν0= 2.47 x 1015 s-1,
δνD = 5.6 x 1010 s-1, δλD = 2.8 x 10-2 Å,

(b)   VIS: For the sodium D line (3P → 3S transition in Na atom) in a sodium vapor cell at temperature T = 1000 K, M = 23, λ = 5891 Å, ν0= 5.1 x 1014 s-1,
δνD = 1.7 x 109 s-1, δλD = 1 x 10-2 Å,

IR: For a vibrational transition between two rovibronic levels (quantum numbers J, v) [(Ji,vi) ↔ (Jk,vk)] of the CO2 molecule in a cell at temperature T = 300 K, M = 44, λ = 10 μm, ν0= 3 x 1013 s-1, δνD = 5.6 x 107 s-1, δλD = 0.19 Å.

Duschinsky effect
In 1937 Russian scientist F. Duschinsky proposed that the mode mixing in the excited electronic state is on e of the main causes of dissymmetry between the absorption and emission spectra. The phenomenon of mode-mixing has been observed in the absorption and emission spectra of benzene, naphthalene, phenanthrene, pyridine, and azulene, etc.

Electron Paramagnetic Spectroscopy
This is a microwave technique based on splitting electronic energy fields in a magnetic field. It is used to determine structures of samples containing unpaired electrons.

 Electron spectroscopy
There are several types of electron spectroscopy, all associated with measuring changes in electronic energy levels.電子光譜術以X光為光源的光電子光譜術也稱為 “electron spectroscopy for chemical analysis (ESCA)” or “X-ray photoelectron spectroscopy (XPS)”.

Fermi’s golden rule
The Fermi’s golden rule is for calculating the rate of stimulated transitions. The transmission rate, W, to a band of states where the number of states per unit energy ρ (referred as the density of states), is given by W = (2π/ħ)|H(1)|2ρ. [費米golden rule是用來計算stimulated躍遷速率的。]

Light emitted from an excited molecule is called fluorescence if the emission mechanism does not require the molecule to pass through a state of different spin multiplicity.

Fourier Transform Spectrosopy
This is a family of spectroscopic techniques in which the sample is irradiated by all relevant wavelengths simultaneously for a short period of time. The absorption spectrum is obtained by applying a mathematical analysis to the resulting energy pattern.

Franck-Condon factor (integral, principle)  [webpage FC]
Because nuclei are much more massive than electrons, an electronic transition takes place while the nuclei are effectively stationary. [由於核子的質量比電子大很多,電子躍遷時可把核子視為靜止的狀態。]

Gamma-ray Spectroscopy
Gamma radiation is the energy source in this type of spectroscopy, which includes activation analysis and Mossbauer spectroscopy.

Gaussian atomic orbital
Atomic orbitals are expressed as the form exp[-ar2]

He-I & He-II light sources (氦-I與氦-II紫外光光源)
He-I 光源的波長為58.4 nm (584
Å),其光子的能量為21.22 eVHe-II光源的波長為30.4 nm (304 Å),其光子的能量為40.80 eV。這兩種光源可用在光電子光譜實驗,例如:Ultraviolet photoelectron spectra of 3-haloanilines, J.L.D. Sky, E.I. von Nagy-Felsobuki, J. Mol. Struct. 522, 95 (2000)。

Hole-burning spectroscopy (燒孔光譜術) [webpage HB]

HOMO, highest occupied molecular orbital 

Hyperconjugation (超共軛)
Hyperconjugation is the overlap of σ and π orbitals on neiboring atoms, such as the methyl C–H σ bonds with the ring π orbitals in methylbenzene.

Infrared Spectroscopy
The infrared absorption spectrum of a substance is sometimes called its molecular fingerprint. Although frequently used to identify materials, infrared spectroscopy also may be used to quantify the number of absorbing molecules.

Intensity stealing (or borrowing)
In the case of a failure of the Born-Oppenheimer approximation, a forbidden transition acquires intensity by virtue of some mixing with states to which transitions are allowed. [B-O近似假設無法描述真實狀況時,原本禁制的躍遷(在光譜中沒有訊號)會因為能階的混合(在光譜中有譜線出現)]

Intermolecular forces
An intermolecular force is a force between molecules and has no further tendency to form chemical bonds. The attractive forces may include the following: [不形成化學鍵的分子間作用力,其中的引力部分可大約歸類為以下幾種型態]

(a) Ion-ion interaction (between charged species): V µ 1/R

(b) Ion-dipole interaction (between ions and polar molecules): V µ 1/R2

(c) Dipole-dipole interaction (between two polar molecules): V µ 1/R3in a solid (when molecules are not rotating) but as V µ 1/R6 in a fluid (in which molecules rotate).

(d) dipole-induced dipole interaction (between a polar molecule and a polarizable molecule [which may or may not be polar]): V µ 1/R6.

(e) induced dipole-induced dipole interaction (between a polarizable molecule and a polarizable molecule [which may or may not be polar]): V µ 1/R6. This is referred as dispersion force or London force. The typical magnitude of the potential energy of the dispersion interaction is about 2 kJ mol-1.

Internal conversion
An internal conversion is a radiationless transition from one molecular state to another of the same multiplicity. It occurs in which collisions cause the higher singlets S2, S3, etc. to make a radiationless transition into the lowest excited singlet state S1, which then fluoresces.

Intersystem crossing
An intersystem crossing is a radiationless transition from one molecular state to another of different multiplicity. An example is the conversion of an excited singlet state into a triplet state.

Ionization energy (adiabatic and vertical)  [webpage IE]

Infrared spectroscopy 
紅外光譜術, 詳細敘述請參看另一網頁 [webpage IR]

Infrared photoinduced Rydberg Ionization (IR-PIRI) spectroscopy 
紅外光誘導雷得堡游離光譜術, 詳細敘述請參看另一網頁 [webpage IR-PIRI]

Jablonski diagram
A Jablonski diagram is a schematic portrayal of the relative positions of the electronic and vibrational levels of a molecule without any attempt being made to show the relative geometrical locations in terms of molecular potential energy curves. The electronic states and the stacks of their vibrational levels are shown schematically. The labels S and T denote the singlet and triplet states of the molecule, respectively. Straight arrows represent radiative transitions, those upwards correspond to absorption and those downwards to emission. Wavy lines between vertical stacks of levels represent radiationless transitions. Those between terms of the same multiplicity are internal conversions and those between terms of different multiplicity are intersystem crossings. Verticle wavy lines within a stack represent relaxation to thermal equilibrium of the vibrational energy as a result of collisions with the surrounding medium. [Jablonski圖用來表達分子的電子能態和振動態的相對關係,但不涉及分子結構和能量的關係,Y軸為相對能階,X軸則無特殊意議。略述於下:(1)其中ST分別代表分子的單重及三重態;(2)帶有箭頭的直線代表輻射躍遷,箭頭向上代表吸光,或箭頭向下代表放光;(3)能階(以水平的直線表示)之間的波狀線代表非輻射躍遷(不吸光也不放光),若是在相同的電子能態(單重態或三重態)則稱為internal conversion,若是在不同的電子能態(例如單重態和三重態之間)就叫作intersystem crossings(4)垂直於能階的波狀線代表(正在被探討的)分子和周圍其他的分子碰撞後,為了達到兩者間的熱平衡,(正在被探討的)分子的振動能量轉換成熱量,此熱量被周圍其他的分子帶走,(正在被探討的)分子原處於高振動能態就會降到較低的振動能態或不振動能態(此過程,分子光譜的術語稱為relaxation)]

Jahn-Teller theorem
In 1937, H. E. Jahn and Edward Teller stated “In a non-linear molecule, there is always a distortion that removes any orbital degeneracy of its electronic state.” The static Jahn-Teller effect is the distortion of obitally degenerate molecules to achieve a lower energy. The dynamic Jahn-Teller effect is the hopping of the distortion from one orientation to another. [原本直線形分子的同能階電子能態,換成是非直線形分子時,電子能態會改變,稱為Jahn-Teller效應。假如非直線形分子的電子能態降低,稱為static Jahn-Teller效應;假如非直線形分子的結構改變,稱為dynamic Jahn-Teller效應。]

JWKB, (Jefferys-Wentzel-Kramers-Brillouin), s semiclassical approximation to quantum mechanics

Kasha’s law
The fluorescent level is the lowest level of the specified multiplicity. [分子會放射螢光時的能態,是某電子能態 (例如單重態或三重態)的最低能階狀態,稱為螢光態。此分子放射螢光後,自高電子能態降到較低的電子能態(相同的multiplicity)]

Koopmans’ theorem
n 1933, Dutch theoretical chemist T. Koopmans proposed, “The ionization energy of an atom or molecule is equal to the energy of the orbital which the electron is ejected” [荷蘭理論化學家Koopmans1933年提出的理論:原子或分子的游離能等於被移出的電子所在軌域的能量。]

Laser Spectroscopy
Absorption spectroscopy, fluorescence spectroscopy, Raman spectroscopy, and surface-enhanced Raman spectroscopy commonly use laser light as an energy source. Laser spectroscopies provide information about the interaction of coherent light with matter. Laser spectrocopy generally has high resolution and sensitivity.

Lorentzian line shape
In 1930 Weisskopf and Wigner used quantum field theory to derive the following theoretical line shape for a transition between states n and m having finite lifetimes:

a / {[(ν-νmn)2+(τn-1m-1)2]/16π2},

where τn and τm are the average lifetimes of states n and m, νmn is the frequency, and a is a constant characteristic of the transition. The general form of a Lorentzian line shape is a / [(ν-ν0)2+b2]. For the Lorentzian line shape, the maximum occurs at ν = ν0 and equals a/b2. For the Weisskopf-Wigner shape, b = (τn-1m-1)2]/4π. If state n is the ground state, thenτn = ¥ and the width of the spectral line measures the uncertainty DEm is the energy of the excited state. Then, DEmτm = ħ/2.

LUMO, lowest unoccupied molecular orbital

Mass analyzed threshold ionization (MATI) spectroscopy [webpage MATI]
質量解析臨界游離光譜術方法相似於卻優於零動能光電子光譜術可提供分子的質量資訊可能是1991年之後最重要的光電子光譜技術, 詳細敘述請參看另一網頁 

Mass Spectrometry
A mass spectrometer source produces ions. Information about a sample may be obtained by analyzing the dispersion of ions when they interact with the sample, generally using the mass-to-charge ratio.

Moment of inertia, Ie =μRe2, (at equilibrium)

Morse potential
In 1929, American theoretical physicist P. M. Morse proposed U(R) = U(Re) + De{1 – exp[-a(R-Re)]}2, where De is the depth of the minimum and a = (ke/2De)1/2ω. [Note that Re, De and ke are referred as the equilibrium internuclear distance, dissociation energy, and force constant, respectively.] For H2 in the ground electronic state, Re = 0.741
ÅDe/hc = 38297 cm-1, ω/(2πc) = 4403.2 cm-1

Mulliken population analysis
If the contribution of an atomic orbital to a molecular orbital is cA, then that orbital contributes –e| cA|2 to the charge density on atom A. The analysis of the distribution of charge in terms of the population of molecular orbitals and the contributing atomic orbitals is known as Mulliken population analysis. 假若利用Gaussian98程式從事量子化學計算,結果會包括此項資訊,例如:利用RHF/6-31++G**計算3-aminopyridine在基態的最佳化結構時,所得在N1, C2, C3, C4, C5, C6, N7(amino)的電核密度分別為-0.239, 0.085, -0.360, 0.127, -0.129, -0.124, -0.548。負數愈大代表該原子周圍的電子密度愈大。

Multiphoton ionization (MPI) spectroscopy
When several photons interact simultaneously with a molecule, multiphoton processes can occur. The multiphoton processes can be used to raise the molecule into one of its excited electronic states, if the photon flux is great enough. The electronically excited molecule is bathed in a very intense field of radiation and can absorb additional photons until it is removed from a resonant condition by ionization, dissociation, reemission of photons, or the end of the light pulse. The wavelength dependence of multiphoton transitions reveals much about the electronic structure of the molecule. For many excited electronic states their most probable fate in an intense field is ionization. A primary advantage of using a multiphoton transition instead of a single-photon transition to determine structure is a difference in selection rules. Although no electronic transition is exactly forbidden, selection rules often cause a transition to be weak. The use of multiphoton techniques to change the relative intensities of different electronic bands is valuable in determining new states and in determining the symmetry and character of transitions of states whose intensities are often masked by congestion and diffuseness in their transitions. The pineering work of (1) P. M. Johnson and coworkers [J. Chem. Phys. 62, 2500 (1975), 62, 4562 (1975), 64, 4143 (1976), 64, 4638 (1976), Acc. Chem. Res. 13, 20 (1980)] and (2) F. W. Dalby and coworkers [Phys. Rev. Lett. 34, 1207 (1975), Can. J. Phys. 55, 1033 (1977), 56, 183 (1978)] demonstrated conclusively that molecules could be efficiently ionized using the MPI technique.

Multiplex or Frequency-Modulated Spectroscopy
In this type of spectroscopy, each optical wavelength that is recorded is encoded with an audio frequency containing the original wavelength information. A wavelength analyzer can then reconstruct the original spectrum.
One-color resonant two-photon ionization (1C-R2PI) spectroscopy [1C-R2PI]
單色共振二光子游離光譜術, 詳細敘述請參看另一網頁
Hydrogen with parallel spins (rotational states with odd J values).
Oscillator strength
The oscillator strength f of a transition is a measure of its intensity. For strongly allowed transitions f is close to 1; for symmetry-forbidden transition f is close to 10-5. 一個躍遷過程的f 可反映至光譜線的強度。
Parabolic potential energy, V = (1/2)kx2
Hydrogen with paired nuclear spins (rotational states with even J values).
A polaron is a defect in an ionic crystal that is formed when an excess of charge at a point polarizes the lattice in its vicinity.
Photoelectron (PE) spectroscopy (光電子光譜術)
光電子光譜術當分子吸收光子的過程中若光子的能量(Ehv)高過於分子的游離能(EI)時分子即被游離(即所謂的光電效應)成離子同時電子也被釋放出來多餘的能量Eexcess = Ehv- EI = 離子態分子的動能(Ekion)+離子態分子的內能(Eiion)+電子的動能(Ek)光電子光譜術即是測量電子的動能(Ek)的技術當分子被游離的瞬間離子和電子(被稱為光電子)同時產生離子和電子以類似"爆炸"式飛離開時由動量守恆的定理得知m1v1 = -m2v2假設1,2分別代表離子和光電子已知離子的質量遠大於光電子(m1>>m2)因此v1<<v2, 並且 Ekion = m1(v1)2 << m2(v2)2 = Ek光電子將帶著動能Ek快速地飛離"爆炸"現場(游離反應中心)一般說來離子態分子的動能(Ekion)很小可被忽略 實驗過程中Ehv光子的能量(Ehv)是已知的由測量的光電子光譜可得知分子的游離能和離子的內能由於轉動能量比振動能量小很多離子的內能常被解釋成離子的振動能量.  光電子光譜術的解析度一般可達~0.01 eV = 10 meV (80 cm-1)
Photoinduced Rydberg Ionization (PIRI) spectroscopy 
光誘導雷得堡游離光譜術詳細敘述請參看另一網頁[webpage PIRI]
PPP, Pariser-Parr-Pople method, a semiemperical procedure
Predissociation is a dissociation that occurs in a transition before the transition limit is attained. It is detected by blurring of the absorption lines followed by the resumption of sharp lines at higher frequency before the onset of the true dissociation limit.
A progression is a series of lines that arise from transitions from the same vibrational level of one of the states (the ground electronic state for absorption) to successive vibrational levels of the other state. E.g. v” = 0, v” = 0, 1,2, …
Pulsed field ionization (PFI)
脈衝場游離是個很重要的技術尤其應用在光電子光譜和臨界游離光譜術方面當分子吸收單個真空紫外光或多個紫外光可能處於高雷得堡態若外加一脈衝電場即可將它游離, 此游離過程即所謂的脈衝場游離
Quantum defect
The quantum defect arises from the effect of the other electrons in the atoms on the electron of interest. It decreases as the principal quantum number of the electron increases, for as n increases the electron is progressively further away from the nucleus and its surrounding core electrons increasingly resemble a single point charge. The quantum defect is a quide to the extent of penetration, but it has little other theoretical significant importance.
Raman process
The Raman process is the inelastic scattering of a photon by a molecule. In Raman scattering the incident photon may lose energy to the molecule by exciting its rotation or vibration, in which case it emerges from the collision with a lower frequency. Alternatively, the photon may acquire energy from the molecule if a mode is already excited and hence energy with a higher frequency. Since molecular rotation and vibration are quantized, the energy transfer can occur only in packets, and so the scattered light contains frequency components that are shifted from the incident frequency by discrete amounts. The frequency composition of the scattered radiation is the Raman spectrum of the molecule.
Raman Spectroscopy
Raman scattering of light by molecules may be used to provide information on a sample's chemical composition and molecular structure.
Reduced mass, μ = (ma•mb) / (ma+mb)
Reduced mass, μ = (ma•mb) / (ma+mb)
Renner-Teller effect (splitting, coupling, or interaction)
The interaction between the ro-vibrational and electron angular momenta is referred to as Renner-Teller interaction, which results in a splitting in the energy levels. One of the simplest cases is that an energy splitting is produced by the interaction of the electronic and vibrational angular momenta. Therefore vibronic coupling (interaction) can lead to a Renner-Teller splitting.

Resonance-enhanced multiphoton ionization (REMPI) spectroscopy
共振加強多光子游離(REMPI)光譜術"共振加強"指分子的游離的過程中會經過特定的中間態此中間態通常為中性分子的電子激發(electronically excited [vibrationless])態或電子激發振動(vibronic)態"多光子"通常指最少的光子數目的光子能量和可超過分子的游離能依實驗課題而定若是研究苯衍生物則只需兩個紫外光子即可達分子的游離臨界因此稱為共振二光子游離(resonant two-photon ionization, R2PI)光譜術因研究目標及現實的實驗設備R2PI又分為單色(只需一套可調波長的脈衝式紫外光雷射)和雙色(需要兩套可調波長的脈衝式紫外光雷射)所以又有所謂的單色共振二光子游離(1C-R2PI)和雙色共振二光子游離(2C-R2PI)光譜術

Rotational constant, Be = h/(8π2Ie) [Note that Ie =μRe2] (for diatomics)

RRK theory, Rice-Ramsperger-Kessel theory
RRK theory, Rice-Ramsperger-Kessel-Marcus theory

Schrödinger equation
In 1926, Austrian theoretical physicist Erwin Schrödinger proposed a equation which, when solved, gives the wavefunction of a system and all the properties of the system. Time-independent Schrödinger equation: = ,  Time- dependent Schrödinger equation: = iħ(ψ/t).

Semiemperical calculation
Semiemperical calculation uses a Hamiltonian simpler than the correct one, and takes some of the integrals as parameters whose values are determined using experimental data. 半經驗式計算法
Spectroscopy is a technique that uses the interaction of energy with a sample to perform an analysis. There are several instruments that are used to perform a spectroscopic analysis. In simplest terms, spectroscopy requires an energy source (commonly a laser, but this could be an ion source or radiation source) and a device for measuring the change in the energy source after it has interacted with the sample (often a spectrophotometer or interferometer).
The data that is obtained from spectroscopy is called a spectrum. A spectrum is a plot of the intensity of energy detected versus the wavelength (or mass or momentum or frequency, etc.) of the energy.
A spectrum can be used to obtain information about atomic and molecular energy levels, molecular geometries, chemical bonds, interactions of molecules, and related processes. Often, spectra are used to identify the components of a sample (qualitative analysis). Spectra may also be used to measure the amount of material in a sample (quantitative analysis).
Stark effect
In 1913, German Physicist Johannes Stark observed the Stark effect which is the modification of the energy levels of atomic and molecular spectra by the application of an electric field.
Stimulated Raman-UV double resonance spectroscopy
拉曼躍遷的機制昇至某一振動能階(系統則處於電子基態振動激發態),造成REMPI光譜訊號減弱或增強,若連續改變光誘導的雷射(稱為pump laser)波長,便可以記錄拉曼光譜(Raman spectroscopy獲得系統在振動模式及能
      這種技術有兩種不同機制,第一種是記錄系統電子基態時因為拉曼躍遷而引起所減弱的離子訊號,稱為Ionization-loss stimulated Raman spectroscopy;另一種則是連續改變光誘導雷射波長記錄因為拉曼吸收而造成的能階躍遷而增強的離子訊號,稱之為:Ionization-gain stimulated Raman spectroscopy

Two-color resonant two-photon ionization (2C-R2PI) spectroscopy
雙色共振二光子游離光譜術詳細敘述請參看另一網頁 [webpage 2C-R2PI]

Time-resolved spectroscopy
       時間解析光譜技術常被用來研究分子團簇內能轉移的動態機制,一般包括兩步驟首先以第一道雷射光(稱為激發雷射pump laser)和系統(分子複合物或團簇)作用系統分子吸收特定波長的光之後,即被激發至電子激發態(此過程稱為電子躍遷),再第二道雷射(稱為探查雷射probe laser)將分子游離(此過程即為共振游離)。當分子系統(通常是多原子的中型或大的分子)電子激發態的分子內振動態時,有時候會發生能量轉移現象,使得振動能(vibrational energy)轉換至移動能(traslational energy),因而造成預解離(predissociation)的現象。因此,當系統位於電子激發態時,會有游離與解離兩種機制相互競爭的現象。
        研究此種分子動態機制的方法,可藉由調整激發雷射與探查雷射之時間延遲(time delay)而得到

Threshold photoelectron (TPE) spectroscopy
臨界光電子光譜術, 偵測在游離臨界之上接近零動能的電子

Ultraviolet photoelectron spectroscopy 
以紫外光為光源的光電子光譜術, 也稱為 “molecular photoelectron spectroscopy”

Ultraviolet spectroscopy
紫外光譜術, 詳細敘述請參看另一網頁 [webpage UV]

Uncertainty principle
In 1927, Werner Heisenberg proposed: “The product of the uncertainties in the simultaneous specifications of two complementary observables can never be less than a small quantity of the order of h”. (ΔpΔx≥ħ/2)

UV-IR double resonance spectroscopy
       由於OH鍵的伸縮振動(stretch vibration)在IR光譜上有很強吸收,結合REMPIIR兩種光譜的優點而發展出的紅外及紫外光雙共振光譜(IR-UV double resonance),被認為是用來研究含氫鍵的分子,複合物(complex)或團簇(cluster)中性及離子態紅外光光譜的有效技術
      紅外及紫外光雙共振光譜(IR-UV double resonance) 是由早期的ion-dip光譜技術發展而來,這種方法應用兩道不同雷射進行實驗,並量測因共振游離所產生的電流(離子所造成的),若是有兩道雷射光頻率差與某一振動能階相同,將會造成激發態的電子產生誘發輻射(stimulated emission)而回到較低能階,造成電流降低現象,以這種方法可得到振動光譜。
       本技術的反應機制是先以可調波長的紅外雷射光來激發系統分子,複合物或團簇,經一定的時間延遲(time delay)後,再以另一紫外雷射光使複合物經共振多光子游離(REMPI)的過程產生離子,若是紅外光光子能量(頻率)與系統在電子基態的振動能量(頻率)相同,將會造成離子訊號減弱,此種方法稱為resonant ion-dip infrared spectroscopy 。連續改變紅外光波長(或頻率)(此步驟的專業術語為"掃瞄"),即可得到系統在電子基態的振動吸收光譜。由於此種方法是以共振多光子游離(REMPI)方式來偵測離子,因此具有物種選擇性(species selectivity),可用研究不同異構物(confomational isomer,或conformer)振動光譜。此外,本技術也可結合其他技術用來進行離子態振動光譜之研究,本網頁另一部分所述的光誘導雷得堡游離光譜術(infrared photoinduced Rydberg Ionization (IR-PIRI) spectroscopy)即是

Vibrational frequency,  ν = (1/2π) •(k/μ)1/2 (for diatomics)

Vibronic transition
A vibronic transition is a simultaneous vibration and electronic transition of a molecule. A vibronically allowed transition is an electronic transition that is made possible by the vibrational motion of a molecule.

Visible spectroscopy
可見光譜術, 詳細敘述請參看另一網頁 [webpage VIS]

The wavefunction, ψ, of a system is the function that contains all the information about its dynamical properties.

A wavepacket is a superposition of wavefunctions that is usually strongly peaked in one region of space and virtually zero elsewhere. The peak of the wavepacket denotes the most likely location of the particle; it occurs where the contributing wavefunctions are in phase and interfere constructively. Elsewhere the wavefunctions interfere destructively, and the net amplitude of the wavepacket is small or zero.

X-ray Spectroscopy
This technique involves excitation of inner electrons of atoms, which may be seen as x-ray absorption. An x-ray fluorescence emission spectrum may be produced when an electron falls from a higher energy state into the vacancy created by the absorbed energy.

ZDO, Zero differential overlap, a semiemperical approximation

Zeeman effect
In 1896 Dutch physicist Pieter Zeeman observed the Zeeman effect which is the splitting of spectral lines into several components by a strong magnetic field.

Zero kinetic energy (ZEKE) spectroscopy [webpage ZEKE

Zero point energy
The zero point energy of a system is the energy of its lowest permitted state。

背景音樂: [Eldelweiss小白花]
上次網頁修改日期: 2006/05/02