Photoexcitation and ionization in acetylene

Machado, L. E.; Leal, E P; Csanak, G.; McKoy, B. V.; Langhoff, P. W.

doi:10.1016/0368-2048(82)85001-9

Cited by 63 publications

(27 citation statements)

References 45 publications

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“…[ [23][24][25][26][27][28]. In particular, features in the photoionization spectrum around 0.4963 hartree in the photon energy are generally associated with the formation and subsequent autoionization of the 3σ g → 3σ u excited state [26,27].…”

Section: B High-order Harmonic Generation: the Ir Pulsementioning

confidence: 99%

High-order harmonic generation from highly excited states in acetylene

Mulholland

Dundas

2018

Phys. Rev. A

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High-order harmonic generation (HHG) from aligned acetylene molecules interacting with mid infra-red (IR), linearly polarized laser pulses is studied theoretically using a mixed quantum-classical approach in which the electrons are described using time-dependent density functional theory while the ions are treated classically. We find that for molecules aligned perpendicular to the laser polarization axis, HHG arises from the highestoccupied molecular orbital (HOMO) while for molecules aligned along the laser polarization axis, HHG is dominated by the HOMO-1. In the parallel orientation we observe a double plateau with an inner plateau that is produced by ionization from and recombination back to an autoionizing state. Two pieces of evidence support this idea. Firstly, by choosing a suitably tuned vacuum ultraviolet pump pulse that directly excites the autoionizing state we observe a dramatic enhancement of all harmonics in the inner plateau. Secondly, in certain circumstances, the position of the inner plateau cut-off does not agree with the classical three-step model. We show that this discrepancy can be understood in terms of a minimum in the dipole recombination matrix element from the continuum to the autoionizing state. As far as we are aware, this represents the first observation of harmonic enhancement over a wide range of frequencies arising from autoionizing states in molecules.

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Section: B High-order Harmonic Generation: the Ir Pulsementioning

confidence: 99%

High-order harmonic generation from highly excited states in acetylene

Mulholland

Dundas

2018

Phys. Rev. A

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“…However, the cut-off energy for this inner plateau is lower than that predicted by the classical three-step model: we attribute this to suppression of ionization from the LUMO+1 due to transitions back to the HOMO-1 [66]. These transitions from the LUMO+1 to the HOMO-1 give rise to a window of enhanced harmonics (harmonics [11][12][13][14][15][16][17][18][19][20][21]. We can show that the inner plateau is due to the 3σ g → 3σ u transition rather than the 2σ u → 4σ g transition by calculating the contribution of each state to the harmonic response using Eq.…”

Section: The Role Of Excited States In Hhgmentioning

confidence: 76%

Probing the role of excited states in ionization of acetylene

Dundas

Mulholland

Wardlow

et al. 2017

Phys. Chem. Chem. Phys.

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Ionization of acetylene by linearly-polarized, vacuum ultraviolet (VUV) laser pulses is modelled using timedependent density functional theory. Several laser wavelengths are considered including one that produces direct ionization to the first excited cationic state while another excites the molecules to a Rydberg series incorporating an autoionizing state. We show that for the wavelengths and intensities considered, ionization is greatest whenever the molecule is aligned along the laser polarization direction. By considering high harmonic generation we show that populating excited states can lead to a large enhancement in the harmonic yield. Lastly, angularly-resolved photoelectron spectra are calculated which show how the energy profile of the emitted electrons significantly changes in the presence of these excited states.

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“…double-bump structure seen around 14 e V in photoionisation of the 17T u orbital of C 2 H 2 . In spite of several recent theoretical (Kreile et al 1981;Machado et al 1982;Levine and Soven 1983;Lynch et al 1984) and experimental (Kreile et al 1981;Unwin et al 1981;Parr et al 1982;Keller et al 1982) studies, we do not as yet have a definitive quantitative understanding of the underlying resonance structure in this region, for example, to what extent the structure is due to shape or autoionising resonances or to some combination of such resonances. Of these studies, those of Levine and Soven (1983) are the most relevant to the results we now discuss.…”

Section: Rl----~r_----_----~------r_----~----_ (A)mentioning

confidence: 99%

Dynamics of Single and Multi-photon Ionisation Processes in Molecules

McKoy¹,

Dixit²,

Dubs³

et al. 1986

Aust. J. Phys.

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Aust. J. Phys., 1986,39,761-77 Single-photon ionisation and resonant multiphoton ionisation studies, which can now be carried out using synchrotron radiation and pulsed dye lasers respectively, are providing important dynamical information on molecular photoionisation. In this paper we discuss some results of our recent studies of several, single-and multi-photon ionisation processes in molecules. The results will be taken from our studies of (i) single-photon ionisation of linear molecules with emphasis on the role of shape and autoionising resonances on these cross· sections, (ii) photoionisation from oriented NiCO as a simple but realistic model of photoemission in adsorbate-substrate systems, and (iii) resonant multiphoton ionisation of H 2 .

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Photoexcitation and ionization in acetylene

Cited by 63 publications

References 45 publications

High-order harmonic generation from highly excited states in acetylene

High-order harmonic generation from highly excited states in acetylene

Probing the role of excited states in ionization of acetylene

Dynamics of Single and Multi-photon Ionisation Processes in Molecules

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Photoexcitation and ionization in acetylene

Cited by 63 publications

References 45 publications

High-order harmonic generation from highly excited states in acetylene

High-order harmonic generation from highly excited states in acetylene

Probing the role of excited states in ionization of acetylene

Dynamics of Single­ and Multi-photon Ionisation Processes in Molecules

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Product

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Dynamics of Single and Multi-photon Ionisation Processes in Molecules