Electron and ion coincidence momentum imaging of multichannel dissociative ionization of ethanol in intense laser fields

Itakura, Ryuji; Hosaka, Koichi*; Yokoyama, Atsushi; Ikuta, Tomoya*; Kannari, Fumihiko*; Yamanouchi, Kaoru*

Progress in Ultrafast Intense Laser Science XI; Springer Series in Chemical Physics, Vol.109, p.23 - 42, 2015/00

https://doi.org/10.1007/978-3-319-06731-5_2

We investigate the multichannel dissociative ionization of ethanol in intense laser fields by the photoelectron-photoion coincidence momentum imaging and identify separately the ionization and subsequent electronic excitation in ethanol. From the energy correlation between a photoelectron and a fragment ion, we reveal the amount of the internal energy gained by ethanol cations from the laser field varies depending on the respective ionization and electronic excitation pathways.

Separation of ionization and subsequent electronic excitation for formation of electronically excited ethanol cation in intense laser fields

Ikuta, Tomoya*; Hosaka, Koichi*; Akagi, Hiroshi; Yokoyama, Atsushi; Yamanouchi, Kaoru*; Kannari, Fumihiko*; Itakura, Ryuji

Journal of Physics B; Atomic, Molecular and Optical Physics, 44(19), p.191002_1 - 191002_5, 2011/10

https://doi.org/10.1088/0953-4075/44/19/191002

Ionization and subsequent electronic excitation occurring within the same laser pulse (400 nm, 96 fs, 1.318 TW/cm) are separately investigated by measuring in coincidence an electron and a product ion produced from CHOH. We reveal that the nascent population in the electronically excited CHOH prepared by the ionization decreases as the laser intensity increases, while the subsequent electronic excitation is enhanced through the resonant electronic transitions. Ionization and electronic excitation mechanisms are described based on the electronic state distributions of CHOH.

Photoelectron-photoion coincidence momentum imaging for dissociative ionization in intense laser fields

Hosaka, Koichi; Itakura, Ryuji; Yokoyama, Keiichi; Yamanouchi, Kaoru*; Yokoyama, Atsushi

no journal, , 

When molecules are exposed to intense laser fields, dissociative ionization is efficiently induced and several decomposition pathways competes. The present study aims at revealing the correlation between the electronic states just after ionization and the following dissociation process. The photoelectron-photoion coincidence momentum imaging (PEPICO-MI) technique enables us to detect photoelectrons and photoions produced in a single event simultaneously. We applied PEPICO-MI to dissociative ionization of ethanol (CHOH), whose branching ratio varies as a function of the laser pulse duration. When ethanol molecules are irradiated with a short laser pulse, photoelectron images strongly depend on the correlated product ions.

Intense laser induced electronic excitation in dissociative ionization of ethanol studied by photoelectron-photoion coincidence momentum imaging

Hosaka, Koichi; Itakura, Ryuji; Yokoyama, Keiichi; Yamanouchi, Kaoru*; Yokoyama, Atsushi

no journal, , 

Momentum correlation between a photoelectron and a fragment ion ejected from ethanol in femtosecond intense laser fields

Itakura, Ryuji; Hosaka, Koichi*; Yamanouchi, Kaoru*; Yokoyama, Atsushi

no journal, , 

In order to clarify the mechanism of dissociative ionization of ethanol in intense laser fields, the correlation maps P(E, E), where E and E denote kinetic energy of an electron and a fragment ion, respectively, are obtained by photoelectron-photoion coincidence momentum imaging. The kinetic energy distribution of the ions at a specific electron kinetic energy of electrons E are reproduced by an exponential curve of exp(-E/E), where E is a variable parameter, suggesting that the intramolecular energy redistribution proceeds efficiently in the course of the dissociation process after the ionization.

Polarization dependence of dissociative ionization of ethanol by intense laser irradiation

Akagi, Hiroshi; Otobe, Tomohito; Itakura, Ryuji; Hosaka, Koichi*; Yamanouchi, Kaoru; Yokoyama, Atsushi

no journal, , 

In the present work, ethanol molecules are irradiated with a circularly-polarized intense laser field (I = 1.4 10 W/cm), and the produced electron and ion are measured in coincidence. The channel-specific photoelectron spectra correlated with the C-C and C-O dissociation channels are similar to that correlated with the parent ion, showing the series of distinctive ATI peaks. These are the signature representing that the electronic ground state of parent ions is initially prepared upon the ionization, and then, the subsequent electronic excitation leading to the C-C or C-O dissociation takes place within the same laser pulse. For the linear polarization with similar laser field intensity (1.7 10 W/cm), the ATI series is also observed, but less pronounced. This means that the electronic excitation of the parent ion is more efficiently induced in the circularly polarized laser field than in the linearly polarized one.

Ionization of ethanol and subsequent electronic excitation in ethanol cation in intense laser fields

Itakura, Ryuji; Ikuta, Tomoya*; Hosaka, Koichi*; Akagi, Hiroshi; Yokoyama, Atsushi; Yamanouchi, Kaoru*; Kannari, Fumihiko*

no journal, , 

Using photoelectron-photoion coincidence technique, we identify two ionization routes of ethanol to the electronic ground state and the electronically excited state of ethanol cation in intense ultraviolet (UV) laser fields (400 nm, 96 fs). The population ratio of the electronically excited state with respect to the electronic ground state of CHOH at the instant of the ionization decreases significantly as the laser intensity increases from 1.3 to 18.1 TW/cm. It is also revealed that the probability of the subsequent electronic excitation of CHOH within the same pulse is enhanced as the laser intensity increases.

Dissociative ionization dynamics of ethanol in intense laser fields; Energy correlation between photoelectron and fragment ion

Itakura, Ryuji; Ikuta, Tomoya*; Hosaka, Koichi*; Akagi, Hiroshi; Yokoyama, Atsushi; Yamanouchi, Kaoru*; Kannari, Fumihiko*

no journal, , 

We investigate dissociative ionization of ethanol induced by intense laser fields using photoelectron-photo ion coincidence momentum imaging. Our attentions are focused on the energy correlation between an electron and a fragment ion produced from an identical ethanol molecule. We reveal that the internal energy gained from laser fields depends on the ionization and fragmentation pathways. We discuss the ionization and dissociation mechanism based on the experimental results depending on the laser characteristics.

Dissociative ionization dynamics of ethanol in intense laser fields by photoelectron-photoion coincidence momentum imaging

Hosaka, Koichi; Itakura, Ryuji; Yokoyama, Keiichi; Yamanouchi, Kaoru*; Yokoyama, Atsushi

no journal, , 

In intense laser fields, molecules are decomposed into fragments through a number of competing dissociative ionization pathways. We investigate the dissociative ionization dynamics of ethanol in intense laser fields with photoelectron-photoion coincidence momentum imaging. The channel-specific photoelectron spectra reveal the electronic states prepared just after ionization, depending both on the decomposition pathways and on the temporal profile of laser pulses.

Fragment momentum specific photoelectron imaging of ethanol in intense laser field

Hosaka, Koichi; Itakura, Ryuji; Yokoyama, Keiichi; Yamanouchi, Kaoru*; Yokoyama, Atsushi

no journal, , 

In intense laser fields, molecules are decomposed into fragments through a number of competing dissociative ionization pathways. We have investigated the dissociative ionization dynamics of ethanol in intense laser fields with photoelectron-photoion coincidence momentum imaging. The fragment momentum specific photoelectron images reveal the correlation between the electronic states prepared just after ionization and the following dissociation dynamics of ethanol cation.