注册 登录  
 加关注
   显示下一条  |  关闭
温馨提示!由于新浪微博认证机制调整,您的新浪微博帐号绑定已过期,请重新绑定!立即重新绑定新浪微博》  |  关闭

tangxiao的博客

以为我是天才

 
 
 

日志

 
 
 
 

Barn (unit)--From Wikipedia, the free encyclopedia  

2012-10-18 16:45:21|  分类: 默认分类 |  标签: |举报 |字号 订阅

  下载LOFTER 我的照片书  |

barn (symbol b) is a unit of area. Originally used in nuclear physics for expressing the cross sectional area of nuclei and nuclear reactions, today it is used in all fields of high energy physics to express the cross sections of any scattering process, and is best understood as a measure of the probability of interaction between small particles. A barn is defined as 10?28 m2 (100 fm2) and is approximately the cross sectional area of a uranium nucleus. The barn is also the unit of area used in nuclear quadrupole resonance and nuclear magnetic resonance to quantify the interaction of a nucleus with an electric field gradient. While the barn is not an SI unit, it is accepted for use with the SI due to its continued use in particle physics.[1] It is one of the very few units that is accepted for use with SI units, and one of the most recent units to have been established (cf. the knot and the bar, other non-SI units acceptable in limited circumstances).[2]

Two related units are the outhouse (1 μb, or 10?34 m2) and the shed (10?24 b (1 yb), or 10?52 m2),[3] although these are rarely used in practice.

  1. ^ "Chapter 4.1: Non-SI units accepted for use with the SI, and units based on fundamental constants"SI brochure (8th edition)BIPM. May 2006. Retrieved 2009-03-13.
  2. ^ "Table 8. Other non-SI units"SI brochure (8th edition).BIPM. May 2006. Retrieved 2009-03-13.
  3. ^ "Nuclear Glossary". Nuclear Glossary. 2004-05-27. Retrieved 2011-04-08.
  评论这张
 
阅读(123)| 评论(0)
推荐 转载

历史上的今天

评论

<#--最新日志,群博日志--> <#--推荐日志--> <#--引用记录--> <#--博主推荐--> <#--随机阅读--> <#--首页推荐--> <#--历史上的今天--> <#--被推荐日志--> <#--上一篇,下一篇--> <#-- 热度 --> <#-- 网易新闻广告 --> <#--右边模块结构--> <#--评论模块结构--> <#--引用模块结构--> <#--博主发起的投票-->
 
 
 
 
 
 
 
 
 
 
 
 
 
 

页脚

网易公司版权所有 ©1997-2018