We're all used thermomoeters to measure temperature but
sometimes we need to measure temperature in places you can't _1_
put a thermometer — for example, inside a rocket engine. One of the best methods for those really hard-to-get-to place _2_
is based on laser spectroscopy. Light from a laser pointing _3_
at the region of interest is absorbed by molecules and some of it are re-emitted back towards the source where it can be _4_
measured. The re-emitted light is shifted in frequency (changed in wavelength) by amounts that depend on the molecule and also the temperature and pressure of the surrounding gas _5_
because of collisions among the molecules. The single, sharp frequency from the laser is thus smeared out into a whole spectrum of frequency whose shape can be used to determine _6_
the temperature provided so that the molecular transitions _7_
and line shapes are known. Because it is the main component of the air, it is convenient to use nitrogen since its molecular _8_
properties are known from room temperature to temperature of about 1，200 degree Celsius from experimental measurements. _9_
Although this is a large range, it is a large range, it is far short of what it is needed for some applications. _10_

答案：

1. places + where

2. place-places

3. pointing- pointed

4. are-is

5 also + on

6. frequency-frequencies

7. provided so that去掉so

8. since-and

9. degree-degrees

10. what it is去掉it