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Journal Articles

Direct ab initio molecular dynamics study of the two photodissociation channels of formic acid

Kurosaki, Yuzuru; Yokoyama, Keiichi; Teranishi, Yoshiaki

Chemical Physics, 308(3), p.325 - 334, 2005/01

https://doi.org/10.1016/j.chemphys.2004.05.032

Times Cited Count：23 Percentile：60.73(Chemistry, Physical)

A total of 1200 trajectories have been integrated for the two dissociation channels of formic acid, HCOOH H $_{2}$ O + CO (1) and HCOOH CO $_{2}$ + H $_{2}$ (2), which occur with 248 and 193 nm photons, using the direct ab initio molecular dynamics method at the RMP2(full)/cc-pVDZ level of theory. It was found that the percentage of the energy distributed to a relative translational mode in reaction 2 is much larger than that in reaction 1. This is mainly due to the difference in the geometry of transition state (TS); the H $_{2}$ O geometry in the TS of reaction 1 was predicted to significantly deviate from the equilibrium one, whereas the CO $_{2}$ and H $_{2}$ geometries in the TS of reaction 2 were found to be more similar to their equilibrium ones. It was also found that the product diatomic molecules, CO and H $_{2}$ , are both vibrationally and rotationally excited. The calculated relative population of the vibrationally excited CO for the 248 nm photodissociation was consistent with experiment.

Journal Articles

Element- and orientation-selective photo-fragmentation using polarized synchrotron radiation

Sekiguchi, Tetsuhiro; Ikeura-Sekiguchi, Hiromi*; Baba, Yuji; Shimoyama, Iwao; Nath, K. G.

Photon Factory Activity Report 2002, Part B, P. 80, 2003/11

http://pfwww.kek.jp/acr2002pdf/part_b/pf02b080.pdf

no abstracts in English

Journal Articles

Orientation effect on phot-fragmentation and ion-desorption from the topmost layers of molecular solids

Sekiguchi, Tetsuhiro; Ikeura, Hiromi*; Baba, Yuji

Surface Science, 532-535(1-3), p.1079 - 1084, 2003/06

Using a newly developed rotatable time-of-flight mass spectrometer(R-TOF-MS) and polarized synchrotron radiation, we have investigated orientation effect on fragmentation and desorption pathways occurring at the top-most layers of molecular solids. Reported will be polarization-angle dependencies of TOF mass spectra, high-resolution electron- and ion-NEXAFS in condensed formic acid, formamide and benzene. For condensed formamide(HCOND $_{2}$ ), marked orientation effect was observed for the enhanced H $^{+}$ -yields following C1s * $_{C-H}$ resonance. Direct photodissociation and charge-neutralization play an important role in the effect. For some fragment species, however, the bond scission showed no polarization dependence when dissociation sites were far from core-excited atoms. This is the case for N-D scission and D $^{+}$ -desorption following C1s excitation, suggesting that indirect process governs, where secondary electrons would induce the fragmentation.