Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Yamakawa, Koichiro; Nasu, Hirokazu*; Shimizu, Genki*
Bunko Kenkyu, 69(3), p.105 - 106, 2020/06
Terahertz and infrared spectroscopy is one of the powerful ways to elucidate the structures and vibrational modes of molecular clusters. We review an experimental apparatus for absorption spectroscopy in an ultra-high vacuum covering the wavenumber range of 60-7000 cm
, from the viewpoints of vacuum-, low-temperature-, and spectroscopy-techniques. We also introduce the terahertz and infrared spectrum of D
O clusters isolated in an Ar matrix measured with this apparatus.
OYamakawa, Koichiro; Nasu, Hirokazu*; Suzuki, Natsumi*; Shimizu, Genki*; Arakawa, Ichiro*
Journal of Chemical Physics, 152(17), p.174310_1 - 174310_13, 2020/05
Times Cited Count：2 Percentile：11.43(Chemistry, Physical)We have established an apparatus for terahertz and mid-infrared spectroscopy in an ultrahigh vacuum and have measured absorption spectra of DO clusters trapped in solid Ar. To assign terahertz absorption peaks due to the DO dimer, trimer, and tetramer, the dependence of the spectrum on the annealing temperature and DO dilution was analyzed. The assignment was also examined by ab initio calculations with use of the ONIOM method, where flexibility of surrounding Ar atoms was systematically incorporated. We identified all of the intermolecular fundamentals of the dimer and those with significant intensities of the trimer and tetramer, whose structural symmetries were revealed to be broken down. After isolating the DO clusters in solid Ar, we sublimated only Ar atoms to leave behind matrix-sublimation ice, which was found to be amorphous- or crystal-like depending on the formation conditions: the dilution and sublimation-temperature. Since the crystallinity got higher with raising the dilution and sublimation-temperature, the diffusion of the DO monomer on the surface of sublimating solid Ar was found to be crucial to the crystallization of the sublimation ice.
Sugimoto, Takeru*; Nasu, Hirokazu*; Arakawa, Ichiro*; Yamakawa, Koichiro
Journal of Chemical Physics, 150(18), p.184302_1 - 184302_5, 2019/05
Times Cited Count：4 Percentile：21.85(Chemistry, Physical)We measured infrared absorption spectra of crystalline II of methane and succeeded in detecting a prominent Q(2) peak by rapid cooling after annealing as well as previously reported rovibrational and librational-vibrational peaks. The integral intensities of the R(0), R(1), and Q(2) peaks were found to show biexponential dependence on time. This clearly demonstrates the interconversion among the three nuclear-spin isomers occupying low-lying rotational levels.
O nanoclusters combined with ONIOM calculationYamakawa, Koichiro; Nasu, Hirokazu*; Arakawa, Ichiro*
no journal, ,
Using an apparatus for terahertz- (THz-) and infrared- (IR-) spectroscopy in an ultrahigh vacuum, we measured absorption spectra of DO nanoclusters isolated in an Ar matrix and examined dependence of the spectrum on the DO dilution and annealing temperature. The dilution of Ar/DO was in the range of 100-1000, and the annealing temperature was increased from 15 K to 25 K. Comparing the spectrum in the THz region with the IR range, where spectral assignments have been well established, we assigned the THz absorption peaks due to the intermolecular fundamentals of (DO)
with 
= 2-4. To support the assignments, we also performed the ab initio calculation with the "our own N-layered integrated molecular orbital and molecular mechanics (ONIOM)" method, where flexibility of surrounding Ar atoms was systematically incorporated.
O iceYamakawa, Koichiro; Shimizu, Genki*; Suzuki, Natsumi*; Nasu, Hirokazu*; Tsuboi, Rei*; Kurahashi, Hiroyuki*; Arakawa, Ichiro*
no journal, ,
no abstracts in English
Yamakawa, Koichiro; Nasu, Hirokazu*; Suzuki, Natsumi*; Shimizu, Genki*; Arakawa, Ichiro*
no journal, ,
Nano-sized molecular clusters have been intensively investigated in a spectroscopic way to reveal the nature of intermolecular interaction. Compared with the infrared (IR) range, only a few spectral measurements in the terahertz (THz) range have been reported, so that the assignment of the vibrational mode to THz absorption was not established even for the water dimer. In the present study, we constructed an experimental apparatus for THz-IR absorption spectroscopy in an ultrahigh vacuum and measured spectra of deuterated-water clusters formed in solid Ar to identify the THz absorption peaks of the dimer, trimer, and tetramer.
