{"created":"2023-06-20T13:21:18.607012+00:00","id":1461,"links":{},"metadata":{"_buckets":{"deposit":"a0333051-9f7a-450a-bcf3-4bd86cabab6d"},"_deposit":{"created_by":21,"id":"1461","owners":[21],"pid":{"revision_id":0,"type":"depid","value":"1461"},"status":"published"},"_oai":{"id":"oai:ir.soken.ac.jp:00001461","sets":["2:427:9"]},"author_link":["0","0","0"],"item_1_creator_2":{"attribute_name":"著者名","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"Md.,Serajul,Islam,Prodhan"}],"nameIdentifiers":[{}]}]},"item_1_creator_3":{"attribute_name":"フリガナ","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"モハメド, セラジュル イスラム プロドハン"}],"nameIdentifiers":[{}]}]},"item_1_date_granted_11":{"attribute_name":"学位授与年月日","attribute_value_mlt":[{"subitem_dategranted":"2009-03-24"}]},"item_1_degree_grantor_5":{"attribute_name":"学位授与機関","attribute_value_mlt":[{"subitem_degreegrantor":[{"subitem_degreegrantor_name":"総合研究大学院大学"}]}]},"item_1_degree_name_6":{"attribute_name":"学位名","attribute_value_mlt":[{"subitem_degreename":"博士（理学）"}]},"item_1_description_12":{"attribute_name":"要旨","attribute_value_mlt":[{"subitem_description":" Two major topics of his thesis are (i) development of the velocity map
imaging (VMI) spectrometer for investigation of the photoion images of
fullerenes, and (ii) simulation studies of possible processes for C60fragmentation.
There are two plausible photofragmentation pathways of excited C60 cations,
namely the stepwise C2-loss and direct fission processes. Several groups have
tried to distinguish these two processes by measuring the total average kinetic
energy release (KER) in the decompositkxr of C60+ into C56+ and smaller
fragments. Such efforts, however, have met with failure. The portion of the KER
partitioned to the ionic fragments was found to be a few tens of
millielectronvolts and is comparable to or smaller than the average thermal
energies of neurtal C60 molecules in an effusive beam. The above two processes
therefore give C56+ and smaller fragments with similar average kinetic energies
in the laboratory system. Obviously, we must measure a precise 3D velocity
distribution, speed and angular distributions, to gain helpful clue to decide on
which process is more dominant. For this purpose we have developed a VMI
spectrometer that is very sensitive to thermal ions having small translational
energies.
Our VMI spectrometer is based on a time-of-flight (TOF) technique for
the fragment ions produced by irradiation of synchrotron radiation. Its basic
performance has been experimentally tested by using five rare gases at photon
energy hv=35 eV. The 3D velocity distributions were reconstructed by using
the inverse Abel transformation (IAT) from measured 2D images projected
on a position-sensitive detector(PSD) to the cross- sectional images in the
perpendicular plane of the spectrometer. Using the speed distributions extracted
perpendicular plane of the spectrometer. Using the speed distributions extracted
from these cross-sectional images, we have evaluated the temperatures by the
least-squares fit of the data points to the Maxwell-Boltzmann distribution. The
best fitted curves of the lighter three rare gases are in reasonable agreement
with the Maxwell-Boltzmann distributions at the temperature T= 300K. The
temperatures obtained by the fittings are 282,272 and 295 K for He, Ne ard Ar,
respectively. Small deviations from the expected value of 300 K can be
accounted for by systematic errors peculiar to the numerical image processing in
the IAT. For Kr and Xe the agreement is much worse mainly due to smaller
signal-to-background ratios. Furthermore, the best fitted curve of Xe appears to
shift by 60 K in the direction of lower speed as compared to the expected
distribution at 300 K. This shift can be explained as that the raw images of Xe
includes not only Xe+ but also Xe2+ signal counts.
We have simulated the images of five rare gases at 300 K to compare with
the experimentally obtained images. From the simulated projections on the PSD
we have obtained the cross-sectional images and speed distributions. The
temperature of He is evaluated to be 287 K from the last-squares fit of the data
points of the simulated speed distribution to the Maxwell-Boltzmann
distribution. Similar simulations were executed for Ne and Ar. All the
temperatures were found to be in good agreement with those from the
experimental images. Moreover, a close inspection of the simulated images
revealed that the defocusing effect due to a definite ionization volume can be
well reproduced by introducing two Gaussian functions as (a) 2σx, = 0.2 and
2σy= 2.8 mm when oven with thickness monitor was not installed inside the
experimental vacuum chamber, (b)2σ, x=1.7 and 2 σ y=3.2mm when oven
with thickness monitor was installed. Here, σ x and σ y are corresponding to the
standard deviations of two Gaussian functions which are called defocusing
parameters.
A novel simulation method has been established for the image of the 3D
velocity distributions of C56+ produced by dissociative photoionization of C60-.
We calculated the arrival positions of C56+ ions, the spatial density functions,
and the projections on the PSD. The 2D cross-sectional images were derived
from the projected images of C56+ ions produced through the stepwise C2- and
C4--loss processes. At T= 0 K a marked difference in the image pattern could be
seen between the two processes but it is almost smeared out under bulk
conditions of C60 at T= 273K owing to the convolution of the thermal velocity
of nascent parent C60+ ions. In contrast, a remarkable difference at T=0 K were
found to remain event at T=785K for the C56+formation in the C60 beams,
because the transverse velocity of the beam is extremely low. The difference in
the image pattern between the two processes permits conclusive
evidence on which mechanism dominates photofragmentation of C60 in the
extreme UV region. We therefore consider that the present VMI spectrometer
will be available for future studies of the excited-state dynamics of fullerene
ions. Experimentally the image of C56+ might be contaminated by the
background dark counts due to impurities such as water, air, and organic
compounds. We have tried to remove the background counts from the measured
2D image by means of deconvolution using the low-pass and Wiener filters.","subitem_description_type":"Other"}]},"item_1_description_18":{"attribute_name":"フォーマット","attribute_value_mlt":[{"subitem_description":"application/pdf","subitem_description_type":"Other"}]},"item_1_description_7":{"attribute_name":"学位記番号","attribute_value_mlt":[{"subitem_description":"総研大甲第1217号","subitem_description_type":"Other"}]},"item_1_select_14":{"attribute_name":"所蔵","attribute_value_mlt":[{"subitem_select_item":"有"}]},"item_1_select_8":{"attribute_name":"研究科","attribute_value_mlt":[{"subitem_select_item":"物理科学研究科"}]},"item_1_select_9":{"attribute_name":"専攻","attribute_value_mlt":[{"subitem_select_item":"07 構造分子科学専攻"}]},"item_1_text_10":{"attribute_name":"学位授与年度","attribute_value_mlt":[{"subitem_text_value":"2008"}]},"item_creator":{"attribute_name":"著者","attribute_type":"creator","attribute_value_mlt":[{"creatorNames":[{"creatorName":"Md., Serajul Islam Prodhan","creatorNameLang":"en"}],"nameIdentifiers":[{}]}]},"item_files":{"attribute_name":"ファイル情報","attribute_type":"file","attribute_value_mlt":[{"accessrole":"open_date","date":[{"dateType":"Available","dateValue":"2016-02-17"}],"displaytype":"simple","filename":"甲1217_要旨.pdf","filesize":[{"value":"294.7 kB"}],"format":"application/pdf","licensetype":"license_11","mimetype":"application/pdf","url":{"label":"要旨・審査要旨","url":"https://ir.soken.ac.jp/record/1461/files/甲1217_要旨.pdf"},"version_id":"78475b7f-a908-405b-aa61-e1cca8663795"},{"accessrole":"open_date","date":[{"dateType":"Available","dateValue":"2016-02-17"}],"displaytype":"simple","filename":"甲1217_本文.pdf","filesize":[{"value":"1.9 MB"}],"format":"application/pdf","licensetype":"license_11","mimetype":"application/pdf","url":{"label":"本文","url":"https://ir.soken.ac.jp/record/1461/files/甲1217_本文.pdf"},"version_id":"e0b79e1f-e587-4767-b3c4-f99a2d7dd676"}]},"item_language":{"attribute_name":"言語","attribute_value_mlt":[{"subitem_language":"eng"}]},"item_resource_type":{"attribute_name":"資源タイプ","attribute_value_mlt":[{"resourcetype":"thesis","resourceuri":"http://purl.org/coar/resource_type/c_46ec"}]},"item_title":"Construction of a Velocity Map Imaging Apparatus and its Application to a Study of Photoionization Processes of C60","item_titles":{"attribute_name":"タイトル","attribute_value_mlt":[{"subitem_title":"Construction of a Velocity Map Imaging Apparatus and its Application to a Study of Photoionization Processes of C60"},{"subitem_title":"Construction of a Velocity Map Imaging Apparatus and its Application to a Study of Photoionization Processes of C60","subitem_title_language":"en"}]},"item_type_id":"1","owner":"21","path":["9"],"pubdate":{"attribute_name":"公開日","attribute_value":"2010-03-25"},"publish_date":"2010-03-25","publish_status":"0","recid":"1461","relation_version_is_last":true,"title":["Construction of a Velocity Map Imaging Apparatus and its Application to a Study of Photoionization Processes of C60"],"weko_creator_id":"21","weko_shared_id":-1},"updated":"2023-06-20T16:03:42.675986+00:00"}