Photoionization and photodissociation dynamics of H2 after (3+1) resonance-enhanced multiphoton ionization via the B 1Σu+ state

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The state that is responsible for the strong one-photon absorption around 200 nm in the vapor absorption spectrum of maleimide and N-methyl maleimide has been investigated using excited-state photoelectron spectroscopy in combination with ab initio calculations. The projection of the wave function of the excited state on the ionic manifold done in this way reveals multiple, vibrationally resolved, ionization pathways to ground- and excited states of the radical cation, which provide direct evidence for electronic couplings with other, lower-lying states. From a comparison of the experimental intensity distribution over the ionic vibrational states with ab initio calculated Franck–Condon factors, we are able to elucidate the role of the various electronically excited states in the ionization process. The experiments also provide the first determination of adiabatic ionization energies in the two molecules. For maleimide values of 10.330 and 10.903 eV are found for D0 and D1, respectively; for N-methyl maleimide D0 is found at 9.897 or, in an alternative interpretation of the spectrum, at 9.676 eV. Calculations and experiment demonstrate that in this molecule the ground ionic state changes its character with respect to maleimide from a lone pair to a π orbital ionization.

Section: Experimental and Theoretical Detailsmentioning

confidence: 99%

Section: Experimental and Theoretical Detailsmentioning

confidence: 99%

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

Steege

Buma

2003

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“…The setups we use have been described in great detail previously 37,38 and will therefore only be summarized briefly here. In our experiments we partly made use of samples seeded into supersonic expansions, but also performed studies using effusive beams.…”

Section: Experimental and Theoretical Detailsmentioning

confidence: 99%

Vibronic coupling in excited states of acetone

Steege

Wirtz

2002

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Photoelectron spectroscopy of Rydberg states of acetone-h 6 and -d 6 populated by two-or three-photon excitation has been employed to unravel the vibronic description of excited-state levels. For the 3p Rydberg states vibronic transitions have been reanalyzed, leading to various reassignments and the observation of hitherto nonreported transitions. In addition, several ionic vibrational frequencies could be determined. At higher excitation energies previously identified, and in the present study newly identified, members of two Rydberg series have been characterized. The ns Rydberg series was explored up to the 8s state, the nd series up to the 7d state. Based upon the unambiguous assignments of vibronic character that we obtain for excited-state levels, various valence-Rydberg and Rydberg-Rydberg vibronic coupling pathways come to light and are analyzed.

“…At the (nϭ3) dissociation limit the closing of the parent ionization channel was observed, accompanied by the opening of the dissociation channel. This phenomenon was probed by (3ϩ1) REMPI ͑resonantly enhanced multiphoton ionization͒ 9 and by ͑XUVϩvisible͒ two-frequency photoionization. 10 The theoretical framework of multichannel-quantumdefect theory ͑MQDT͒, developed to explain features of coupling to continuum states, was refined by Jungen et al to accurately reproduce the observations on states of u symmetry 11 and of g symmetry.…”

Section: Introductionmentioning

confidence: 99%

Tunneling and decay dynamics of H̄ 1Σg+ outer well states in hydrogen

Reinhold

Hogervorst

Ubachs

2000

We present an experimental study of the decay dynamics of rovibrational states confined in the outer minimum of the HH 1 ⌺ g ϩ potential of the hydrogen molecule. Specific (v,J) quantum states are populated using a two-step excitation process involving a pulsed extreme ultraviolet laser source. Decay products are selectively probed with additional laser pulses, using the timing of these pulses to determine lifetimes. The competition between dissociation and ionization, occurring at short internuclear distance after tunneling through the potential barrier, is addressed. Observed lifetimes and decay channels of H levels are consistent with a semiclassical description of tunneling of the nuclear motion through the potential barrier towards small internuclear distance. For the HD isotopomer breaking of the gϪu symmetry is found to strongly affect the decay dynamics.