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Laboratory submillimeter-wave spectroscopy of interstellar deuterated molecules : evolution timescale determination of dark cloud cores

星际氘化分子的实验室亚毫米波光谱：暗云核心的演化时间尺度测定

基本信息

批准号：
12440161
负责人：
SAITO Shuji
金额：
$ 10.37万
依托单位：
Fukui University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

项目摘要

The main subject of the present proposal is high-sensitivity submillimeter-wave spectroscopy of interstellar deuterides, aiming to estimate the chemical evolutionary age of dark cloud cores from the degree of deuterium fractionation. The following results are obtained during three years proposed.1. The present high-sensitivity submillimeter-wave spectrometer covering up to 600 GHz was improved to cover a new frequency region of 500-830 GHz, aided by the present Grant-in Aid and other sources. The new spectrometer was used to study a few interstellar deuterides given below.2. The proposed method of estimating the chemical evolutionary age of dark cloud cores from the degree of deuterium fractionation is applied to two dark cloud cores, cyanopolyyne peak and ammonia peak, of Taurus Molecular Cloud 1, using the abundance ratios between DC0^+ and HCO^+ combined with the new standard model network of gas-phase chemical reactions. The difference in deuterium fractionation between the two cor … More es is explained by a time difference in the evolutionary age of more than 10^5 yr. This is the first example of the chemical evolutionary age of dark cloud cores estimated from the degree of deuterium fractionation.3. The method proposed above is also applied to two cloud cores, the northeast NH_3 core and the southern NH_3 core, of L134N which is a typical dark cloud having no energy sources. An analysis including the degree of deuterium fractionation and C/0 depletion in cores shows that the southern core is in a more evolved stage than the northeast core. The C/0 depletion also indicates the degree of core evolution. The existence of highly fractionated NH_2D and NHD_2 recently detected at the southern core is consistent with the high C/0 depletion in the southern core.4. Two interstellar deuterides, HDC1^+ and PHD were studied with a new high-sensitivity submillimeter-wave spectrometer. Spectral patterns of PHD were very complicated due to fine and hyperfine structures of phosphorus, hydrogen and deuterium nuclei. A detailed analysis of complicated spectral lines resulted in a precise determination of the hyperfine coupling constants of phosphorus, hydrogen, and deuterium. The principal axis and principal values of the magnetic dipole coupling tensors of hydrogen in PH_2 and deuterium in PD_2 were derived from the observed values of PHD, PH_2 and PD_2. The principal axis of the hydrogen magnetic coupling tensor in PH_2 makes an angle of 2.3^0 with the PH bond. This result is one of rare cases in which a relation between the hyperfine coupling tensor and the related chemical bond is clearly indicated. Less

本提议的主要内容是高灵敏度的星际氚的亚毫米波光谱，目的是根据氘的分馏程度来估计暗云核的化学演化年龄。在提出的三年时间里，取得了以下成果。目前覆盖高达600 GHz的高灵敏度亚毫米波光谱仪经过改进，在现有的助学金和其他来源的帮助下，覆盖了500-830 GHz的新频率区域。新的光谱仪被用来研究下面给出的几个星际氢化物。利用DC0+和HCO2+的丰度比，结合新的气相化学反应标准模型网络，对金牛座分子云1的两个暗云核--氰化聚乙烯峰和氨峰，应用了所提出的从氚分馏程度估算暗云核化学演化年龄的方法。两种COR-…中重氢分馏的差异更多的ES可以用进化年龄超过10^5岁的时间差来解释。这是第一个从氘的分馏程度估计暗云核的化学演化年龄的例子。该方法也适用于L134N这一典型的无能源暗云的两个云核，即东北NH_3核和南部NH_3核。分析了岩心中的氚分馏程度和C/O亏损程度，结果表明，南部岩心比东北岩心处于更演化的阶段。C/0耗竭也指示了核心演化的程度。最近在南部岩芯检测到的高分馏NH_2D和NHD_2的存在与南部岩心高C/O亏损相一致。用一台新型的高灵敏度亚毫米波光谱仪研究了两种星际氢化物HDCl~+和PHD。由于磷、氢和氚原子核的精细和超精细结构，PHD的光谱模式非常复杂。通过对复杂谱线的详细分析，精确地确定了磷、氢和氢的超精细耦合常数。根据PHD、Ph_2和Pd_2的观测值，求出了氢在PH_2中的磁偶极耦合张量的主轴和主值。在PH_2中的氢磁耦合张量的主轴与PH键成2.3度角。这一结果是明确指出超精细耦合张量与相关化学键之间关系的罕见情况之一。较少