M. P. Docker

Bio: M. P. Docker is an academic researcher. The author has contributed to research in topics: Hyperfine structure & Propynal. The author has an hindex of 1, co-authored 2 publications receiving 36 citations.

Nuclear hyperfine structure in the electronic spectrum of propynal

Abstract: The laser‐induced fluorescence spectrum of propynal (S1←S0) (A 1A‘←X 1A’) has been investigated and a series of perturbations due to singlet–triplet coupling resolved. The singlet–triplet interaction matrix elements are of the order of 280 MHz. Fluorescence decays for both the mixed singlet–triplet eigenstates have been measured and are shown to contain quantum beats due to coherent excitation of nuclear hyperfine levels. This Doppler‐free measurement in the time domain leads to an accurate determination of the nuclear hyperfine splittings produced by the two nonequivalent hydrogen atoms. The hyperfine structure has been analyzed for two rotational levels in the 91 vibrational state and gives the following values for combinations of the Fermi contact constants and dipole–dipole constants of the two protons in the pure triplet state: T1(a 3A‘): A(1)FC+ 1/2 (T(1)xx−T(1)yy) ∼46 MHz; A(2)FC+ 1/2 (T(2)xx−T(2)yy) −4 MHz; T(1)zz∼T(2)zz ∼0 MHz. A simple model for the spin distribution in propynal predicts that...

Rovibronic level structure of electronically excited acetylene (A1Au) in a supersonic jet as studied by laser-induced fluorescence and Zeeman quantum beat spectroscopy

Abstract: Laser-induced fluorescence (LIF) spectra of the A 1Au- X 1Σg+ transition of jet-cooled acetylene were measured resolution to resolve the respective rovibronic levels in the A nv′3 vibrational states. Most of rotational levels of the nv′ and 4) state split into several levels, while level splitting occurs scarcely for those in the 2v′3 state. The observed radiative lifetimes of the respective levels are different from each other. Especially, the average lifetime of levels in the 3v′3 state is relatively long compared with those in the other states. The fluorescence from a number of levels decays in an oscillatory manner under a weak magnetic field. This phenomenon is attributed to a coherent interaction between the Zeeman sublevels, from which a magnetic moment, i.e., a g-factor, can be determined characteristic to each level. A large g-factor assigned to a level implies that the level couples strongly with a triplet state. Long lifetimes and large g-factors found for levels in the 3v′3 state imply that these levels couple with triplet states more efficiently than other levels in the 4v′3 or 2v′3 state. Besides the Zeeman quantum beat, a quantum beat ascribed to level anticrossing between a level in the A nv′3 state and a nonfluorescent level is found for a number of excited levels. These anticrossings are due to interaction with its strength of the order of MHz, and ascribed to couplings with vibrationally highly excited levels in the X state.

A study of the singlet–triplet perturbations in the à 1Au state of acetylene by high resolution ultraviolet spectroscopy

Abstract: Laser‐induced fluorescence spectra of the 330 K10 and 340 K10 vibronic bands of the A 1Au←X 1Σ+g transition in acetylene have been recorded with a resolution of 18 MHz. Each rotational transition consists of a group of lines due to coupling of the electronically excited singlet state with isoenergetic triplet states. Using the standard deconvolution procedure the singlet–triplet coupling elements and the density of coupled triplet states are derived for rotational levels up to J=4 in both bands. From the density of coupled triplet states it is concluded that the A 1Au state is perturbed by the T1 3B2 state. Magnetic field measurements have shown that the predissociation of acetylene in the 4ν3’ vibrational level of the A state is caused by a coupling via the T1 3B2 state with predissociating vibrational levels of the electronic ground state.

Quantum beat spectroscopy of molecules

Abstract: This review deals with molecular high-resolution spectroscopy based on the quantum beat phenomenon. Applications of the essentially Doppler-free quantum beat technique are presented with special emphasis on the theoretical description. After an historical introduction and a general discussion of interference experiments, we discuss the expressions to describe the time-resolved fluorescence of a molecule following well defined laser excitation. Our general treatment for the characterization of the excited superposition state enables us to demonstrate the versatility of the method by identifying the excited molecular eigenstates with, for example, Zeeman levels or fine- and hyperfine-structure levels. In addition to the spectroscopic applications of quantum beat experiments in determining molecular structure parameters, we address the applications to molecular dynamics and statistical properties of molecular level structures.

Molecular quantum beat spectroscopy

Abstract: The present account of high-resolution molecular quantum beat spectroscopy emphasizes the versatility of this powerful Doppler-free method. Illustrations are drawn from work on the six-atomic molecule propynal carried out in the authors' laboratory. Examples of anisotropic Zeeman, Stark and hyperfine quantum beats, of isotropic molecular quantum beats and of multi-level quantum beats are discussed with regard to intramolecular relaxation dynamics and the determination of structural parameters such as nuclear hyperfine constants, electric dipole moments, spin-orbit matrix elements and asymmetry-splittings.