彗星C/1999S4 (LINEAR) のNH3のスピン温度について
H Kawakita1, J Watanabe, H Ando
1Gunma Astronomical Observatory, 6860-86 Nakayama, Takayama, Agatsuma, Gunma 377-0702, Japan. kawakita@astron.pref.gunma.jp
まとめ
彗星C/1999S4 (LINEAR) のアンモニアのオーソ対比比は,土星と天王星の間に氷が形成されたことを示唆しています. これは太陽の星雲についての手がかりを提供します.
科学分野:
- 天文学と天体物理学について
- 惑星科学は惑星科学である.
- 彗星科学 彗星科学
背景:
- 彗星の組成は,初期の太陽系についての洞察を提供します.
- アンモニアは,太陽の星雲から発生した彗星の重要な揮発性物質です.
- アンモニアのオルト・トゥ・パラ比 (OPR) は,その形成温度の敏感なトレーサーである.
研究 の 目的:
- 彗星C/1999S4 (LINEAR) のNH2のオーソ対比比 (OPR) を決定する.
- 彗星のアンモニア氷の形成温度と位置を推測する.
- 太陽の星雲の中の彗星氷の熱史と起源を理解するために.
主な方法:
- 彗星C/1999S4 (LINEAR) の高分散光学スペクトルが,スバル望遠鏡を用いて得られた.
- 光刺激モデルを使用してNH2排出線を分析した.
- オーソ対パラ比 (OPR) を計算し,アンモニアのスピン温度を導出しました.
主要な成果:
- 信号と騒音の比率が高いスペクトルは,正確なNH2排出線を生成しました.
- NH2のオーソ対パラ比 (OPR) は3.33±0.07と決定された.
- アモニアの導出スピン温度は28 ± 2ケルビンであった.
結論:
- NH2 OPRは原始アンモニアOPRを反映し,形成条件を示しています.
- 導出されたスピン温度は,土星と天王星の間に形成された彗星のアンモニア氷を示唆しています.
- この発見は,初期の太陽星雲における分子形成と凝縮の位置を制限する.
関連する概念動画
Atomic Nuclei: Nuclear Spin State Overview
NMR-active nuclei have energy levels called 'spin states' that are associated with the orientations of their nuclear magnetic moments. In the absence of a magnetic field, the nuclear magnetic moments are randomly oriented, and the spin states are degenerate. When an external magnetic field is applied, the spin states have only 2 + 1 orientations available to them. A proton with = ½ has two available orientations. Similarly, for a quadrupolar nucleus with a nuclear spin value of one, the...
Atomic Nuclei: Nuclear Spin State Population Distribution
Near absolute zero temperatures, in the presence of a magnetic field, the majority of nuclei prefer the lower energy spin-up state to the higher energy spin-down state. As temperatures increase, the energy from thermal collisions distributes the spins more equally between the two states. The Boltzmann distribution equation gives the ratio of the number of spins predicted in the spin −½ (N−) and spin +½ (N+) states.
Spin–Spin Coupling Constant: Overview
In bromoethane, the three methyl protons are coupled to the two methylene protons that are three bonds away. In accordance with the n+1 rule, the signal from the methyl protons is split into three peaks with 1:2:1 relative intensities. The methylene protons appear as a quartet, with the relative intensities of 1:3:3:1.
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must have a...
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must have a...
Spin–Spin Coupling: One-Bond Coupling
Coupling interactions are strongest between NMR-active nuclei bonded to each other, where spin information can be transmitted directly through the pair of bonding electrons. While nuclei polarize their electrons to the opposite spins, the bonding electron pair has opposite spins. Configurations with antiparallel nuclear spins are expected to be lower in energy. When coupling makes antiparallel states more favorable, J is considered to have a positive value. The one-bond coupling constant, 1J,...
Spin–Spin Coupling: Two-Bond Coupling (Geminal Coupling)
Two NMR-active nuclei bonded to a central atom can be involved in geminal or two-bond coupling. Geminal coupling is commonly seen between diastereotopic protons in chiral molecules and unsymmetrical alkenes, among others.
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
The central atom need not be NMR-active because its electrons are affected by the electron polarization of the spin-active atoms. However, spin information is transmitted less effectively than in one-bond coupling, and 2J values are usually weaker than 1J values. The energy of...
¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR
The axial and equatorial protons in cyclohexane can be distinguished by performing a variable-temperature NMR experiment. In this process, except for one proton, the remaining eleven protons are replaced by deuterium. The deuterium substitution avoids the possible peak splitting caused by the spin-spin coupling between the adjacent protons. The remaining proton flips between the axial and equatorial positions.

![Measuring the Spin-Lattice Relaxation Magnetic Field Dependence of Hyperpolarized [1-13C]pyruvate](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F59399.jpg&w=3840&q=50)
