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Journal Articles

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

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.

Journal Articles

Correlation between a photoelectron and a fragment ion in dissociative ionization of ethanol in intense near-infrared laser fields

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

Journal of Chemical Physics, 138(20), p.204301_1 - 204301_9, 2013/05

 Times Cited Count:12 Percentile:44.57(Chemistry, Physical)

Dissociative ionization of ethanol (C$$_{2}$$H$$_{5}$$OH) induced by an intense near-infrared laser pulse are investigated using photoelectron-photoion coincidence method. It is shown that both the electronic ground state and the first electronically excited state of C$$_{2}$$H$$_{5}$$OH$$^{+}$$ are produced at the moment of photoelectron emission. From the observed correlation between the electronic states of C$$_{2}$$H$$_{5}$$OH$$^{+}$$ prepared at the moment of photoelectron emission and the kinetic energy release of the fragment ions, it is revealed that C$$_{2}$$H$$_{5}$$OH$$^{+}$$ prepared in the electronic ground state at the photoelectron emission gains larger internal energy in the end than that prepared in the electronically excited state. The averaged internal energy of C$$_{2}$$H$$_{5}$$OH$$^{+}$$ just before the dissociation is found to increase when the laser field intensity increases from 9 to 23 TW/cm$$^{2}$$. And when the laser pulse duration increases from 35 to 800 fs.

Journal Articles

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

 Times Cited Count:8 Percentile:39.78(Optics)

Ionization and subsequent electronic excitation occurring within the same laser pulse (400 nm, 96 fs, 1.3$$sim$$18 TW/cm$$^{-2}$$) are separately investigated by measuring in coincidence an electron and a product ion produced from C$$_{2}$$H$$_{5}$$OH. We reveal that the nascent population in the electronically excited C$$_{2}$$H$$_{5}$$OH$$^{+}$$ 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 C$$_{2}$$H$$_{5}$$OH$$^{+}$$.

Journal Articles

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

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

Chemical Physics Letters, 475(1-3), p.19 - 23, 2009/06

 Times Cited Count:11 Percentile:35.14(Chemistry, Physical)

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.

Oral presentation

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 (C$$_{2}$$H$$_{5}$$OH), 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.

Oral presentation

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.

Oral presentation

Dissociative ionization 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.

Oral presentation

Dissociative ionization dynamics of ethanol in intense laser fields studied 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 afterionization, depending both on the decomposition pathways and on the temporal profile of laserpulses.

Oral presentation

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.

Oral presentation

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, , 

Oral presentation

Fragment ion momentum resolved photoelectron imaging of ethanol in intense laser fields

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

no journal, , 

no abstracts in English

Oral presentation

Dissociative ionization of oxygen in intense laser fields studied by photoelectron photoion coincidence momentum imaging

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

no journal, , 

no abstracts in English

Oral presentation

Photoelectron-photoion coincidence imaging for dissociative ionization of ethanol in intense UV laser fields

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

no journal, , 

Recently, using a photoelectron-photoion coincidence momentum imaging apparatus, we found two possible pathways for the dissociative ionization of ethanol in intense NIR laser fields: one pathway is the direct access to the electronically excited states leading to the dissociation, the other is the stepwise excitation through the ionization to the electronic ground state. In this study, we investigate the dissociative ionization in intense UV laser with the same technique and compare the results with those with the NIR pulses.

Oral presentation

Electronic excitation dynamics of molecules ionized in intense laser fields studied by photoelectron-photoion coincidence momentum imaging

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

no journal, , 

By the photoelectron-photoion coincidence momentum imaging, channel-specific photoelectron images of ethanol and oxygen molecules ionized in intense laser fields are obtained at different laser field intensities and pulse durations for clarifying their electronic excitation mechanisms.

Oral presentation

Dissociative ionization of ethanol by circularly-polarized ultrashort intense laser fields

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

no journal, , 

When a molecule is exposed to circularly-polarized laser fields, dissociation processes following ionization proceed differently from the case of linearly polarization. In the present work, ethanol molecules are irradiated with a circularly-polarized intense laser field (I = 1.4$$times$$10$$^{13}$$ W/cm$$^{2}$$, $$lambda$$ $$sim$$800 nm), and the produced electron and ion are measured in coincidence. Under the present experimental conditions, Keldysh parameter $$gamma$$ is calculated to be 2.6, suggesting the multiphoton ionization is expected to be dominant. The relative yields of C$$_{2}$$H$$_{4}$$OH$$^{+}$$, CH$$_{2}$$OH$$^{+}$$, and C$$_{2}$$H$$_{5}$$C$$^{+}$$ with respect to the parent ion are 0.36, 0.31, and 0.01, which correspond to only 0.5, 0.4, and 0.2 of those for the linear polarization with similar laser field intensity (1.7$$times$$10$$^{13}$$ W/cm$$^{2}$$.

Oral presentation

Dissociative ionization of ethanol in circularly-polarized intense laser fields

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

no journal, , 

When a molecule is exposed to circularly-polarized laser fields, dissociation processes following ionization proceed differently from the case of linearly polarization. In the present work, ethanol molecules are irradiated with a circularly-polarized intense laser field (I = 1.4$$times$$10$$^{13}$$ W/cm$$^{2}$$, $$lambda$$ $$sim$$800 nm), and the produced electron and ion are measured in coincidence. The relative yields of C$$_{2}$$H$$_{4}$$OH$$^{+}$$, CH$$_{2}$$OH$$^{+}$$, and C$$_{2}$$H$$_{5}$$C$$^{+}$$ with respect to the parent ion are 0.36, 0.31, and 0.01, which correspond to only 0.5, 0.4, and 0.2 of those for the linear polarization with similar laser field intensity (1.7$$times$$10$$^{13}$$ W/cm$$^{2}$$), showing that the polarization change from linear to circular significantly suppresses the C-H, C-C, and C-O dissociation processes.

Oral presentation

Polarization dependence of ionization dynamics of ethanol in intense laser fields

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$$_{0}$$=(1.1$$pm$$0.2) $$times$$ 10$$^{13}$$ W/cm$$^{2}$$, $$lambda$$$$sim$$ 800 nm], 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 show the series of distinctive above-threshold ionization (ATI) peaks, which are similar to those correlated with the parent ion production and C-H dissociation channels. These features imply that the electronic ground state of the parent ion is initially prepared at the moment of the ionization. On the other hand, for the linear polarization, the ATI series is less pronounced, and a diffuse structure become a dominant, which means that the electronically excited states of the parent ion are produced directly on the ionization. Based on the theoretical prediction, we will discuss the polarization dependence of the ionization dynamics.

Oral presentation

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$$_{elec}$$, E$$_{ion}$$), where E$$_{elec}$$ and E$$_{ion}$$ 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$$_{elec}$$ are reproduced by an exponential curve of exp(-E$$_{ion}$$/E$$_{0}$$), where E$$_{0}$$ is a variable parameter, suggesting that the intramolecular energy redistribution proceeds efficiently in the course of the dissociation process after the ionization.

Oral presentation

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

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

no journal, , 

When ethanol molecules are irradiated with an intense UV pulse (400 nm,100 fs, I = 10 TW/cm$$^{2}$$), channel-specific photoelectron momentum images correlated with C$$_{2}$$H$$_{5}$$OH$$^{+}$$, C$$_{2}$$H$$_{4}$$OH$$^{+}$$, CH$$_{2}$$OH$$^{+}$$, and C$$_{2}$$H$$_{5}$$$$^{+}$$ show different features, suggesting that different electronic and vibrational state distributions are prepared upon the ionization for the respective product ion channels.

Oral presentation

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

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

no journal, , 

When ethanol molecules are irradiated with an intense UV pulse (400 nm, 100 fs, 15$$sim$$33 TW/cm$$^{2}$$), channel-specific photoelectron momentum images correlated with C$$_{2}$$H$$_{5}$$OH$$^{+}$$, C$$_{2}$$H$$_{4}$$OH$$^{+}$$, CH$$_{2}$$OH$$^{+}$$, and C$$_{2}$$H$$_{5}$$$$^{+}$$ show different features, suggesting that different electronic and vibrational state distributions are prepared upon the ionization for the respective product ion channels. Basically, the electronic ground state and the first electronically excited state are prepared upon the ionization, and then the subsequent interaction between the ion and the laser field takes place, leading to the respective reaction channels.

27 (Records 1-20 displayed on this page)