The smallest energy transitions are between rotational levels; the next smallest between vibrational levels.是什么意思？

The smallest energy transitions are between rotational levels; the next smallest between vibrational levels.

在转动能级之间的能量跃迁最小, 其次是振动能级之间的跃迁.

the

art. 指已提到的人（物），指说话人与听者已知的人（物），用于独一无二的事物前，与形容词最高级和序数词连用；

例句
He did have a real knowledge of the country...
他对该国的确知之甚多。

smallest

adj. 小的( small的最高级 )，小气的，（服装、食品、家用设施等）小号的，小规模的；

例句
When launched, the Macintosh was the smallest desktop computer ever produced.
当初上市的时候，麦金塔电脑是所有台式电脑里最小的。

energy

n. [物]能量，活力，精力，精神；

例句
A household radiator absorbs energy in the form of electric current and releases it in the form of heat.
家用取暖器吸收电流能量，再以热量的形式释放出来。

transitions

n. 过渡，转变，变迁( transition的名词复数 )；

例句
...a computer program which weights the different transitions according to their likelihood...
根据可能性的大小对不同转换进行加权处理的电脑程序

are

vi. （用于第二人称单复数现在时，第一、三人称复数现在时）是；n. 公亩（等于100平方米）；

例句
We are scared to abandon ourselves to our feelings in case we seem weak or out of control.
我们不敢放纵自己的情感，以免显得太过软弱或缺乏自制。

between

prep. 在…之间，私下，暗中，在…中任择其一，来往于…之间；adv. 当中，中间；

例句
How big is the abyss between what you think you are and what you actually are?
你对自己的认识和真实的你之间差别到底有多大？

rotational

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例句
Mundry uses the same principle for three layered systems with linear expansion or rotational symmetry.
穆恩德瑞将同一原理应用于具线性延伸或转动对称的三层状系统.

levels

n. 水平( level的名词复数 )，水平线，水平仪，水平测量；

例句
Victoria Falls has had above average levels of rainfall this year...
维多利亚瀑布今年的降雨量超过了平均水平。

next

adj. 紧接在后的，次于的，贴近的，紧邻的；adv. 接下去，然后，居后地，依次的；n. 下一位，下一个；prep. 靠近，居于…之后，在…的隔壁；

例句
Constant rain forced the abandonment of the next day's competitions.
连绵阴雨致使翌日各项赛事被迫中止。

vibrational

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例句
Antisymmetric nonresonant vibrational Raman scattering of Tetrahydrofuran ( THF ) is experimentally and theoretically studied in this paper.
研究了四氢呋喃 ( THF ) 非共振拉曼光谱中反对称散射的贡献.