Excited and ionic states of formamide: An excited-state photoelectron spectroscopy and ab initio study

Abstract

. (2002). Excited and ionic states of formamide: an excited-state photoelectron spectroscopy and ab initio study. Journal of Chemical Physics, 117, 8270. DOI: 10.1063/1.1513456 General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. High-resolution excited-state photoelectron spectroscopy has been applied to unravel the spectroscopic and dynamic properties of the excited states of formamide populated by two-and three-photon excitation. In combination with ab initio calculations, this approach has led to various reassignments of previously observed states, and to the observation of new states. One of the aspects that particularly emerges from the present study is the important role of vibronic coupling, which leads to states of heavily mixed character. Projection on the ionic manifold-as is done in our studies-is, however, able to determine the various contributions of the wave function. Our studies have enabled us as well to resolve an apparent disagreement concerning the values of the ionization energies of the ground and first excited state of the radical cation. We find here adiabatic values of 10.233Ϯ0.008 and 10.725Ϯ0.020 eV, respectively. A final issue our studies shed light on concerns the vibrational properties of the ground state of the radical cation.

Spectroscopy and dynamics of excited states in maleimide and N-methyl maleimide: Ionic projection and ab initio calculations

“…We have demonstrated that the complementary approach of concentrating on the energy resolution in the frequency domain-as opposed to time resolution in the time domain-enables one to disentangle vibronically coupled states as well. 1,2,6 As might be expected, these studies show that the frequency domain approach has its own distinct advantages, in particular for close-lying states that ionize to the same electronic ionic state. Application to complementary ionization channels has, however, not been done so far, but is one of the subjects of interest in the present study on maleimide and N-methyl maleimide.…”

“…26 There it was seen that a limited number of molecular orbitals are important for the description of the lower excited states of the neutral molecule. Preliminary ab initio calculations performed by us confirmed this picture: for maleimide of C 2v symmetry it was found that the relevant orbitals are the symmetric n o ϩ (a 1 ) and antisymmetric n o Ϫ (b 2 ) combinations of the lone pair orbitals on the oxygen atoms, a CvC bonding orbital (b 1 ) that we will label as CvC , a orbital (b 1 ) that has a dominant contribution from the nitrogen atom and is labeled as N , and an antibonding * orbital (a 2 4 . On the basis of their electronic description, we can anticipate that the equilibrium geometry and force fields of the states of interest (S 1 to S 4 ) are different.…”

Low-energy electron collisions with formamide using theR-matrix method

“…The experimental data on the basic properties for the ground-state formamide, such as ionization potential (IP) and dipole moment (μ), are also available. The adiabatic IP (V ion a ) and vertical IP (V ion v ) have been determined by photoelectron spectroscopy (V ion a = 10.23 eV [20,21] and V ion v = 10.42 eV [21]). The μ value at the electronic ground state is 1.461 a.u., obtained by the Stark effect measurements [22].…”

Excited state properties of formamide in water solution: An ab initio study

“…In particular, it is known that the solvent environment affects the ground and excited states of formamide leading to significant alterations both in its geometry and in its electronic and vibrational spectra. [4][5][6][7][8][9] The absorption spectrum of the gas-phase formamide molecule has been measured by several groups 4,[10][11][12][13][14][15] and, in the energy range between 5 eV and 10 eV, it presents five main structures, typical of amides, historically labeled W, R 1 , V 1 , R 2 , and Q.…”

“…12,16 Because of the simplicity of formamide and its importance as a model for more complex systems, also numerous theoretical works have been devoted to the study of its excited state properties and of the effects of solvation. 8,11,12,15,[17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] In the literature, different model approaches addressing the computational treatment of the solvent can be found. Typically, continuum, semicontinuum or discrete models are used.…”