Half-width - Hanchihaba

Japanese: 半値幅 - ハンチハバ

When a physical quantity measured against a certain variable forms a symmetrical or nearly symmetrical mountain-shaped curve, the width at half the height of that curve is called the width. For example, in the absorption curve of an electronic spectrum, the molar extinction coefficient ε is plotted on the vertical axis and the wave number on the horizontal axis, and the wave number at 1/2 of ε _max is _+1/2 (high wavenumber side), When it is set to _-1/2 (low wavenumber side), the half-width Δ _1/2 is

Δ _1/2 = _+1/2 - _-1/2
It is sometimes defined as

_max - _-1/2 or _+1/2 - _max
The half-width is sometimes taken as twice the value of the height. In the case of infrared absorption spectra, the same half-width γ as above is used, with absorbance on the vertical axis. The half-width indicates the sharpness of the absorption band, but is mainly used to approximately calculate the area intensity. In NMR (nuclear magnetic resonance) spectra, there are three methods for determining the width of an absorption curve obtained by integrating a differential curve, i.e., a wide-width NMR spectrum, one of which is the half-width method. In this case, as above, half the value of the height is taken as the half-width Δ H _1/2 . For circular dichroism curves, the half-width at the maximum of positive circular dichroism is used. In gas chromatography and liquid chromatography, the area of a chromatogram peak is calculated when performing quantitative analysis, and one method is to use the product b _1/2 × h of the half-width b _1/2 and the height h of the peak.

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

Japanese:

ある変数に対して測定される物理量が，左右対称，あるいはほぼ対称な山形の曲線をなすとき，その1/2の高さにおける幅．たとえば，電子スペクトルの吸収曲線では，図の縦軸にモル吸光係数εを，横軸に波数をとり，ε_max の1/2の波数を_＋1/2(高波数側)，_－1/2(低波数側)とするとき，半値幅Δ _1/2は

Δ _1/2 ＝ _＋1/2 － _－1/2
で定義される．ときには，

_max － _－1/2 または _＋1/2 － _max
の2倍をとって半値幅にすることがある．赤外吸収スペクトルの場合も，縦軸に吸光度をとって上と同じ半値幅γが用いられる．半値幅は吸収帯の鋭さの度合を表すが，主として面積強度を近似的に計算するときに用いられる．NMR(核磁気共鳴)スペクトルでは，微分型の曲線を積分して得られる吸収型の曲線，すなわち広幅NMRスペクトルの幅を求めるのに三つの方法があり，その一つが半値幅法である．この場合も上と同様，高さの1/2の値を半値幅Δ H_1/2とする．円二色性曲線では正の円二色性の極大に関する半値幅が用いられる．ガスクロマトグラフィーおよび液体クロマトグラフィーでは，定量分析を行う際にクロマトグラムのピークの面積を求めるが，その一つの方法として，半値幅 b_1/2 とピークの高さhの積 b_1/2×hが用いられる．