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Journal Articles

The Photoelectron spectroscopic study of the hydrated complex of HONTA + HNO$$_{3}$$

Miyazaki, Yasunori; Adachi, Junichi*; Masuda, Ryotaro*; Gejo, Tatsuo*; Hoshino, Masamitsu*

Photon Factory Activity Report 2021 (Internet), 2 Pages, 2021/00

no abstracts in English

Journal Articles

Fluorescence decay processes following resonant 2p photoexcitation of Ar atoms and clusters studied using a time-resolved fluorescence and photoion coincidence technique

Gejo, Tatsuo*; Ikegami, Takeshi*; Homma, Kenji*; Harries, J.; Tamenori, Yusuke*

Journal of Physics B; Atomic, Molecular and Optical Physics, 46(7), p.075102_1 - 075102_9, 2013/04

 Times Cited Count:3 Percentile:19.12(Optics)

Journal Articles

Long-lived, highly excited neutral hydrogen atom production following oxygen 1s photoexcitation of gas-phase water molecules

Harries, J.; Gejo, Tatsuo*; Homma, Kenji*; Kuniwake, Miki*; Sullivan, J. P.*; Lebech, M.*; Azuma, Yoshiro*

Journal of Physics B; Atomic, Molecular and Optical Physics, 44(9), p.095101_1 - 095101_7, 2011/05

 Times Cited Count:9 Percentile:44.14(Optics)

Journal Articles

Dissociation and recapture dynamics in H$$_2$$O following O 1s inner-shell excitation

Gejo, Tatsuo*; Oura, Masaki*; Kuniwake, Miki*; Homma, Kenji*; Harries, J.

Journal of Physics; Conference Series, 288, p.012023_1 - 012023_7, 2011/04

 Times Cited Count:11 Percentile:91.67

In this paper we present a study of the dissociation dynamics following O 1s inner-shell excitation/ionization in the water molecule. When the O 1s electron is excited just below or just above the ionization threshold, neutral fragments are created. Information on the electronic states of these fragments provides information on the dissociation dynamics. Excitation of the O 1s electron creates a H$$_2$$O$$^+$$ ionic core, which is unstable and undergoes Auger decay. The resulting H$$_2$$O$$^{2+}$$ ion core subsequently dissociates into 2 or three fragments, to one of which the initially excited electron attaches. If this fragment is O$$^+$$ or OH$$^+$$, a neutral, excited O atom can be created. This fragment can undergo further Auger (autoionisation) decay. Here we have analysed the kinetic energy distribution of both these low energy electrons and also the initial high energy Auger electron, obtaining new information on the processes involved.

Oral presentation

Production of neutral particles following O 1s excitation of H$$_2$$O; H$$^*$$ yield and kinetic energy, and ion-H$$^*$$ coincidence studies

Harries, J.; Iseda, Mitsuhiro*; Kuniwake, Miki*; Homma, Kenji*; Gejo, Tatsuo*; Sullivan, J. P.*; Azuma, Yoshiro*

no journal, , 

We report here on studies where metastable H$$^{*}$$ atoms and VUV photons are detected following the O 1s excitation of H$$_2$$O. The studies reveal new information not accessible with ion or electron techniques. The studies are performed using pulsed soft X-ray synchrotron radiation at SPring-8's BL27SU. Metastable particles and VUV photons are directly detected using 2 MCP detectors, and the arrival times of the particles are recorded relative both to each other and to the pulses of incoming radiation. The technique allows the separation of VUV and metastable particle yield, and the study of fluorescence lifetimes. The time-resolved detection of Lyman-$$alpha$$ radiation allows the determination of the population distribution of excited H atoms.

Oral presentation

Metastable H atoms from O 1s excitation/ionisation of H$$_2$$O

Harries, J.; Kuniwake, Miki*; Gejo, Tatsuo*; Homma, Kenji*; Sullivan, J. P.*; Azuma, Yoshiro*

no journal, , 

We report here on studies where metastable H$$^*$$ atoms are directly detected following the O 1s inner-shell excitation of the water molecule, revealing new information not accessible with the ion or photon techniques. Metastable H$$^*$$ yield differs to partial/total ion yields and H$$^*$$ fluorescence yield most strikingly near threshold, where a large peak is observed due to the capture of a Rydberg electron or slow photoelectron by a dissociation H$$^+$$ ion, analogous to a similar observation for N$$^*$$ production from N$$_2$$. The nature of the process is investigated by comparing the kinetic energies of H$$^+$$ and H$$^*$$ fragments, and also by detecting H$$^*$$ in coincidence with H$$^+$$, OH$$^+$$, and O$$^+$$ ions.

Oral presentation

The Ionisation dynamics of water following oxygen 1s inner-shell excitation

Kuniwake, Miki*; Homma, Kenji*; Gejo, Tatsuo*; Asakura, Yuka*; Harries, J.

no journal, , 

When a molecule is irradiated with soft X-rays, an inner-shell electron is excited, leading to the creation of inner-shell vacancy states. De-excitation occurs via processes such as Auger decay and fluorescence. Water is a simple 3-atom molecule, and while its inner-shell excitation processes have been widely studied, there have been few studies on its photo-ionisation dissociation dynamics. Earlier work at SPring-8 revealed the importance of the production of neutral particles in this excitation region. In order to study in detail the production mechanism for metastable atoms, we have compared the kinetic energies of the metasable atoms with those of H ions, and found that they have different excitation photon energy dependencies.

Oral presentation

O1s excitation of gas-phase water; Highly-excited neutral fragments and lifetime-resolved fluorescence

Harries, J.; Kuniwake, Miki*; Homma, Kenji*; Gejo, Tatsuo*; Sullivan, J. P.*; Azuma, Yoshiro*

no journal, , 

Long-lived, highly-excited neutral hydrogen atoms are produced near the O 1s edge of the water molecule. This metastable yield has been studied, along with the kinetic energy of the particles. The excited particles also can decay via fluorescence to the ground state, and by lifetime-resolved detection of the fluorescence new information on the dissociation dynamics can be obtained.

Oral presentation

The Decay routes of argon clusters studied using time-resolved fluorescence

Gejo, Tatsuo*; Iseda, Mitsuhiro*; Homma, Kenji*; Harries, J.; Tamenori, Yusuke*

no journal, , 

When a cluster undergoes inner-shell excitation, as well as electrons and ions fluorescence photons can also be detected. Depending on the excited state, the lifetime of this fluorescence is different, and so recording the arrival times of the photons relative to the exciting radiation, information can be obtained on the excited state distribution. This technique has previously been applied to the helium atom and water molecule, and is applied to clusters for the first time here. For argon clusters there are broadly two lifetime components, and their origin is discussed.

Oral presentation

The Photodissociation dynamics of water following O 1s inner-shell excitation

Kuniwake, Miki*; Harries, J.; Homma, Kenji*; Gejo, Tatsuo*

no journal, , 

When the O 1s electron of a water molecule is excited, Auger decay and dissociation occurs. Near threshold, the Auger electron is faster than the photo-electron, a post-collision interaction (PCI) occurs, and the photoelectron can be recaptured by either the parent ion or a fragment ion. Here we use Auger electron spectroscopy to investigate this process.

Oral presentation

Photodissociation dynamics of water in K-edge energy region

Gejo, Tatsuo*; Kuniwake, Miki*; Homma, Kenji*; Harries, J.; Oura, Masaki*; Sullivan, J. P.*; Azuma, Yoshiro*

no journal, , 

Exciting an inner-shell electron of a molecule to just-above or just-below its ionisation limit provides a system where the Born-Oppenheimer principle is no longer valid, and a valuable opportunity for studying the interaction of the unstable ion core and a low-energy electron. When the ion core undergoes Auger decay and fragments, the initially excited electron can be recaptured. It is the aim of this research to understand what happens in the case of the water molecule, by (1) detecting excited H atoms produced when the electron is captured by an outgoing proton. (2) detect the Lyman-$$alpha$$ radiation produced when these excited H atoms decay, and (3) analysing the energy of low-energy Auger electrons emitted when the electron is captured by an O$$^+$$ or O$$^{++}$$ fragment.

Oral presentation

O(1s) photodissociation dynamics of gas-phase H$$_2$$O

Harries, J.; Gejo, Tatsuo*; Kuniwake, Miki*; Homma, Kenji*; Oura, Masaki*; Sullivan, J. P.*; Azuma, Yoshiro*

no journal, , 

Photo-excitation of the O 1s electron in H$$_2$$O can lead to the production of neutral, excited H atoms. Knowledge of the excited state distribution provides information on the dissociation dynamics process. Excitation of the O 1s electron leads to a H$$_2$$O$$^+$$ ion core. Auger decay subsequently leads to H$$_2$$O$$^{2+}$$, which dissociates, and one of the fragments can capture the initially excited electron. If this fragment is H$$^+$$, excited neutral H atoms are formed. In this research we use pulsed synchrotron radiation as the excitation source, and detect the UV fluorescence emitted when the excited H atoms decay. Analysis of the decay lifetimes leads to information on the excited state distribution.

Oral presentation

The Photodissociation dynamics of H$$_2$$O after recapture process via Auger decay of O 1s inner-shell excitation

Gejo, Tatsuo*; Oura, Masaki*; Kuniwake, Miki*; Homma, Kenji*; Harries, J.

no journal, , 

In this research we have obtained new information on the photo-dissociation dynamics of the water molecule following O (1s) inner-shell excitation/ionisation. When the O 1s electron is excited as well as neutral excited H atoms, highly-excited O and OH fragments can also be produced. By investigating which states these fragments are in information can be obtained on the dissociation routes. When the inner-shell O 1s electron is excited/ionised, an H$$_2$$O$$^+$$ ion core is formed. This is unstable, and Auger decay occurs. The resulting H$$_2$$O$$^{2+}$$ ion core dissociates, and one of the fragments can capture the initially excited electron. When this fragment is O$$^+$$, a neutral O atom is formed. This fragment can undergo further Auger decay, resulting in the production of an electron with low kinetic energy. In this research these electrons are detected and energy analysed.

Oral presentation

Lifetime-resolved H$$^{*}$$ fluorescence following O(1s) excitation/ionisation in gas-phase water molecules

Harries, J.; Gejo, Tatsuo*; Sullivan, J. P.*; Azuma, Yoshiro*

no journal, , 

In this research we have obtained new information on the photo-dissociation dynamics of the water molecule following O (1s) inner-shell excitation/ionisation. When the O 1s electron is excited neutral excited H atoms can be produced. By investigating which states these H atoms are information can be obtained on the dissociation routes. When the inner-shell O 1s electron is excited/ionises, an unstable H$$_2$$O$$^+$$ ion core is formed. This is unstable, and Auger decay occurs. The resulting H$$_2$$O$$^{2+}$$ ion core dissociates, and one of the fragments can capture the initially excited electron. When this fragment is H$$^+$$, a neutral H atom is formed. In this research we use the pulsed nature of synchrotron radiation to study the lifetimes of the fluorescing excited states produced.

Oral presentation

Study on the electronic structure of HONTA for minor actinide separation

Masuda, Ryotaro*; Otaka, Saki*; Gejo, Tatsuo*; Takeuchi, Satoshi*; Adachi, Junichi*; Hoshino, Masamitsu*; Toigawa, Tomohiro; Miyazaki, Yasunori; Sano, Yuichi; Takeuchi, Masayuki

no journal, , 

no abstracts in English

Oral presentation

Study on the electronic structure of HMNTA as a model extractant for minor actinide recovery

Miyazaki, Yasunori; Sano, Yuichi; Takeuchi, Masayuki; Hoshino, Masamitsu*; Gejo, Tatsuo*; Adachi, Junichi*

no journal, , 

no abstracts in English

Oral presentation

The Synchrotron radiation study on the electronic structure of gold-plate HONTA by VUV and soft X-ray irradiations

Miyazaki, Yasunori; Hoshino, Masamitsu*; Gejo, Tatsuo*; Adachi, Junichi*; Takahashi, Osamu*

no journal, , 

${it N,N,N',N',N'',N''}$-hexaoctylnitrilotriacetamide (HONTA) is one of the extractants that form complexation with minor actinides (Am$$^{3+}$$, for example). The initial reaction of radiolysis, whether it is direct or indirect, is ionization of HONTA after interaction with electrons. In this study, VUV and soft X-ray were irradiated to HONTA on the gold plate, and the released electrons were energy analyzed and detected by SCIENTA to acquire the photoelectron spectra. The quantum chemical calculations were performed to evaluate the electronic structure and ionization energy of HONTA. For future works, these results will be applied to the molecular dynamics simulation in order to elucidate radiolysis.

Oral presentation

Investigation of the molecular structure of HONTA in the n-dodecane media by soft X-ray absorption spectroscopy and quantum chemical calculation

Miyazaki, Yasunori; Toigawa, Tomohiro; Gejo, Tatsuo*; Kumaki, Fumitoshi*; Adachi, Junichi*; Nagasaka, Masanari*

no journal, , 

18 (Records 1-18 displayed on this page)
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