The predissociation mechanisms of the e 1Πu and the b′ 1Σu+ states of N2

A theoretical analysis is given of the photofragment anisotropy of long-lived vibrational states as a function of the rotational level and as a function of the predissociation mechanism. The anisotropy of the lower rotational levels is a strong analytical tool for the identification of the electronic symmetry in the final continuum state. Experiments have been performed on the (4pπ)e 1Πu(v=0) Rydberg state and b′ 1Σu+(v=16) valence state in molecular nitrogen using fast beam translational spectroscopy. The rotational levels of the e 1Πu state yield both N(4S)+N(2P) and N(4S)+N(2D) products. We found different angular distributions for 4S+2P and 4S+2D fragments, although originating from the same rotational level. The observed anisotropy parameters, also called β parameters, have been interpreted and point to the presence of complex predissociation pathways involving mixing with known nearby bound and continuum states. The b′ 1Σu+(v=16) state produces dominantly 4S+2D fragments. We give a suggestion for th...

[1]  Richard N. Zare,et al.  Angular Momentum: Understanding Spatial Aspects in Chemistry and Physics , 1988 .

[2]  D. Shemansky,et al.  Medium resolution studies of extreme ultraviolet emission from N2 by electron impact: the effect of predissociation on the emission cross section of the b 1Πu state , 1990 .

[3]  P. Cosby,et al.  Product branching in predissociation of the e 1Πu, e’ 1Σ+u, and b’ 1Σ+u states of N2 , 1989 .

[4]  I. Kovacs,et al.  Rotational structure of the spectra of diatomic molecules , 1972 .

[5]  P. Cosby,et al.  N(4S0), N(2D0), and N(2P0) yields in predissociation of excited singlet states of N2 , 1993 .

[6]  K. Dressler.  The lowest valence and Rydberg states in the dipole-allowed absorption spectrum of nitrogen - A survey of their interactions. , 1969 .

[7]  W. J. Zande,et al.  The derivation of photofragment angular distributions in homonuclear diatomic molecules , 1991 .

[8]  R. Bersohn,et al.  ORIENTATION OF TARGETS BY BEAM EXCITATION. , 1969 .

[9]  H. Scheingraber,et al.  State-Selective Spectroscopy in a Molecular Nitrogen Discharge by Use of Optogalvanic Double-Resonance Spectroscopy , 1983 .

[10]  P. Kleiber,et al.  Quantum state‐selected photodissociation of K2(B 1Πu←X 1Σ+g): A case study of final state alignment in all‐optical multiple resonance photodissociation , 1995 .

[11]  U. Fano,et al.  Impact Excitation and Polarization of the Emitted Light , 1973 .

[12]  Robert W. Field,et al.  Perturbations in the Spectra of Diatomic Molecules , 1986 .

[13]  C. Jonah.  Effect of Rotation and Thermal Velocity on the Anisotropy in Photodissociation Spectroscopy , 1971 .

[14]  J. Durup,et al.  Angular distributions and separation energies of predissociation photofragments of O2+ (b 4Σg−, v′=4, N′, F′) , 1979 .

[15]  Paul H. Krupenie,et al.  The spectrum of molecular nitrogen , 1977 .

[16]  Cosby,et al.  Predissociation quantum yields of singlet nitrogen. , 1994, Physical review. A, Atomic, molecular, and optical physics.

[17]  M. Kakimoto,et al.  High-resolution optogalvanic study of the c4(0)1Πu, c′5(0)1Σu+, and a″(0)1Σg+ Rydberg states of N2 , 1982 .

[18]  Ajello,et al.  Medium-resolution studies of extreme ultraviolet emission from N2 by electron impact: Vibrational perturbations and cross sections of the c4' 1 Sigma u+ and b' 1 Sigma u+ states. , 1989, Physical review. A, General physics.

[19]  E. C. Zipf,et al.  On the dissociation of nitrogen by electron impact and by E.U.V. photo-absorption , 1978 .

[20]  S. J. Singer,et al.  Theory of diatomic molecule photodissociation: Electronic angular momentum influence on fragment and fluorescence cross sections , 1983 .

[21]  P. K. Carroll,et al.  The cn 1 Π u and cn' 1 Σ u+ Rydberg states of N2: high resolution studies , 1972 .

[22]  K. Aw,et al.  Measurement of the lifetime of the metastable a" 1 Sigma g+ state of N2. , 1991 .

[23]  P. K. Carroll,et al.  The high energy 1 Σ u+ states of N2 , 1970 .

[24]  D. E. Freeman,et al.  High resolution vacuum ultraviolet absorption spectrum of N2: Perturbations in the and c4(0) 1Πu Rydberg levels , 1984 .

[25]  K. Dressler,et al.  Nonadiabatic representations of the 1Σ+u and 1Πu states of the N2 molecule , 1983 .