Pyrazine photoelectron spectrum

In the ultraviolet photoelectron spectrum, the most readily ionized level of pyridine is the nonbonding orbital (with contributions from the o -framework). The three diazines show two lone-pair levels, with the greatest splitting in the case of pyridazine but considerable also in pyrimidine and pyrazine. These long-distance splittings are attributed to both through-space and through-bond interactions, particularly the latter. 

The photoelectron spectrum of pyridazine is similar to those of pyrazine, pyrimidine, and triazine i.e., the lowest ionization potential corresponds to ionization of a lone-pair electron. The ionization potential is in agreement with the calculated value. These spectra were recorded also of pyridazine 1-oxide and 1,2-dioxide, and it was found that the perturbation of the t-system by the N—O group results in the separation of the lower excited states of the AT-oxide ions. ... 

Interestingly, a conical intersection very similar to that of the S i(n7r ) and S 2(7T7r ) neutral excited states has been found for the n and n hole states of the pyrazine cation.A linear vibronic-coupling model has been constructed for the and states of the pyrazine cation employing many-body Green s function methods for the calculation of the vibronic-coupling parameters. The ah initio calculated photoelectron spectrum of the Ag n ) and states is compared in Fig. 7 with the... 

Fig. 7. Experimental Hel UV photoelectron spectrum of pyrazine (a) and calculated spectrum (b), showing the X Ag and B g bands. The envelope in (b) represents the convolution of the theoretical spectrum with a typical experimental resolution function (reproduced from Ref. 116).

The property of interest here is a spectrum, either an absorption spectrum (pyrazine) or photoelectron spectrum (butatriene and allene). The spectrum [Pg.596]

Calculations of the ion yield in dependence on the pulse delay time At and on the parameters of the laser pulses have been performed in Refs. 86 and 93 for simple one-dimensional models of excited-state vibrational motion and vibronic coupling. It has been found that for the vibronic-coupling examples considered and for suitably chosen pulse parameters, the ion signal as a function of At maps very well the adiabatic electronic population probability. As an example of a molecular system comprising conical intersections. Sec. 5.1 presents a calculation of the time-resolved photoelectron spectrum of pyrazine. 

Fig. 7. Time-resolved photoelectron spectrum as obtained for the four-mode model of pyrazine, assuming 40 fs pump and probe pulses. Shown are the contributions (a) /22(Bfc, At) and (b) In Ek,A.t), stemming from the ionization of the S2 and Si states of pyrazine, respectively, as well as (c) the total spectrum, defined in Eq. (79).

Pyrazine forms an azeotrope with water [60% pyrazine-40% water, b.p. 95.5° (uncorr.) (760mmHg) /ip 1.4510] (578). A method of assay for pyrazine and some common impurities has been developed (579). The dipole moment (Debye units) of pyrazine has been determined in dioxane, cyclohexane, and benzene as zero (580, cf. 581) and it has also been calculated as zero (133, 582). The e.s.r. spectrum (583) and the polarized single-crystal absorption spectra of pyrazine (and tetramethylpyrazine) (584) have been recorded. The photoelectron spectra of pyrazine and tetramethylpyrazine have been determined and suggest a different behavior towards electrophilic attack in the two cases (585). 

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