367 research outputs found
Cold collisions of heavy molecules with alkali-metal atoms in a magnetic field: Ab initio analysis and prospects for sympathetic cooling of SrOH by Li(S)
We use accurate ab initio and quantum scattering calculations to explore the
prospects for sympathetic cooling of the heavy molecular radical
SrOH() by ultracold Li atoms in a magnetic trap. A two-dimensional
potential energy surface (PES) for the triplet electronic state of Li-SrOH is
calculated ab initio using the partially spin-restricted coupled cluster method
with single, double and perturbative triple excitations and a large
correlation-consistent basis set. The highly anisotropic PES has a deep global
minimum in the skewed Li-HOSr geometry with cm and saddle
points in collinear configurations. Our quantum scattering calculations predict
low spin relaxation rates in fully spin-polarized Li+SrOH collisions with the
ratios of elastic to inelastic collision rates well in excess of 100 over a
wide range of magnetic fields (1-1000 G) and collision energies
(10~K) suggesting favorable prospects for sympathetic cooling of
SrOH molecules with spin-polarized Li atoms in a magnetic trap. We find that
spin relaxation in Li+SrOH collisions occurs via a direct mechanism mediated by
the magnetic dipole-dipole interaction between the electron spins of Li and
SrOH, and that the indirect (spin-rotation) mechanism is strongly suppressed.
The upper limit to the Li+SrOH reaction rate coefficient calculated for the
singlet PES using adiabatic capture theory is found to decrease from ~cm/s to a limiting value of cm/s with
decreasing temperature from 0.1 K to 1 K
電界蒸発機構の解明によるアトムプローブ顕微鏡の高精度化、及び表面反応顕微鏡の開発
学位の種別: 課程博士審査委員会委員 : (主査)東京大学教授 尾張 眞則, 東京大学教授 宮山 勝, 東京大学教授 藤岡 洋, 東京大学教授 高木 紀明, 金沢工業大学教授 谷口 昌宏University of Tokyo(東京大学
CO mapping of the nuclear region of NGC 6946 and IC 342 with Nobeyama millimeter array
CO observations of nearby galaxies with nuclear active star forming regions (and starburst galaxies) with angular resolutions around 7 seconds revealed that molecular bars with a length of a few kiloparsecs have been formed in the central regions of the galaxies. The molecular bar is interpreted as part of shock waves induced by an oval or barred potential field. By shock dissipation or dissipative cloud-cloud collisions, the molecular gas gains an infall motion and the nuclear star formation activity is fueled. But the distribution and kinematics of the molecular gas in the nuclear regions, which are sites of active star formation, remain unknown. Higher angular resolutions are needed to investigate the gas in the nuclear regions. Researchers made aperture synthesis observations of the nuclear region of the late-type spiral galaxies NGC 6946 and IC 342 with resolutions of 7.6 seconds x 4.2 seconds (P.A. = 147 deg) and 2.4 seconds x 2.3 seconds (P.A. = 149 deg), respectively. The distances to NGC 6496 and IC 342 are assumed to be 5.5 Mpc and 3.9 Mpc, respectively. Researchers have found 100-300 pc nuclear gas disk and ring inside a few kpc molecular gas bars. Researchers present the results of the observations and propose a possible mechanism of active star formation in the nuclear region
Multichannel quantum defect theory with a frame transformation for ultracold molecular collisions in magnetic fields
We extend the powerful formalism of multichannel quantum defect theory
combined with a frame transformation (MQDT-FT) to ultracold molecular
collisions in magnetic fields. By solving the coupled-channel equations with
hyperfine and Zeeman interactions omitted at short range, MQDT-FT enables a
drastically simplified description of the intricate quantum dynamics of
ultracold molecular collisions in terms of a small number of short-range
parameters. We apply the formalism to ultracold Mg + NH collisions in a
magnetic field, achieving a 10-fold reduction in computational effort
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