JPH067122B2 - How to know the diameter of an atom or molecule - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel analytical method to which a magnetic field precedent double-focusing mass spectrometry is applied.

(B) Conventional technology Although many analytical methods are already in practice in the field of instrumental analysis, it is not possible to elucidate the composition or molecular structure of an arbitrary substance by any one of the instrumental analysis methods. Only by combining analytical methods can the composition and molecular structure be elucidated. In daily analysis work, there are many identification analyzes that determine whether or not a sample is the same as a specific substance, but even in this case, two types of substances are generally judged to be the same substance if the results obtained by a single analysis method are the same. Cannot be done and it is necessary to combine several analytical techniques. Mass spectrometry, which is one of the instrumental analyses, is similar, and its power is exhibited only when it is combined with other analytical methods.

(C) Purpose of the present invention is to apply a magnetic field precedent type double-focusing mass spectrometer to obtain sample information which is completely different from the information about the sample conventionally obtained by this type of apparatus.

D. Configuration for Ma using a magnetic field precedent type double focusing mass spectrometer
ss Analyzed Ion Kinetic E
There is a method called energy spectrum (MIKES). The present invention is a modification of this method to obtain information on the size of an atom or molecule.
Will be briefly described. The figure shows a magnetic field-preceding double-focusing mass spectrometer. M is a magnetic field for mass analysis, E is an electric field for energy analysis, and S is an ion source that ionizes sample molecules. I
s is an ion source slit, and the ionized sample molecules are accelerated and made to enter the magnetic field M from the ion source slit Is, and the ions having a specific mass determined by the magnetic field are converged on the intermediate point I between the magnetic field M and the electric field E. A collision material C is arranged so as to surround the convergence point I. There are holes in the front and back of the collision chamber C so that the ions having the specific mass can pass through the collision chamber C. An appropriate gas such as He or Ar is supplied into the collision chamber C and is maintained at a pressure of about 0.001 to 1 Torr. Ions that converge at point I collide with the molecules of this gas and split. The velocity of the ions does not change before and after this split. That is, it is assumed that the ion converging at the point I is A ⁺ , its velocity is ν (which is a vector pointing to the right in the figure), and as a result of the splitting, it is divided into an ion A ′ ⁺ and a molecule A ″. A ⁺ = A ′ ⁺ + A ″ At this time, both A ′ ⁺ and A ″ have the same velocity ν that A ^{+ originally} had. The split ion A ′ ⁺ thus generated is The energy is analyzed by being incident on the electric field E for energy analysis.
Since there are multiple stages of the process in which fragmented fragments further collide with gas molecules and are fragmented, various fragment ions are generated, but these have the same velocity and different mass, so they have different kinetic energies. Therefore, one spectrum can be obtained by energy analysis. This spectrum is related to how the original ions split by collisions with gas molecules and provides information about the sample molecules. This is MIKE
This is the principle of S.

In the above-mentioned method, the probability that the ions of the sample molecules that have entered the collision chamber C will collide with the gas molecules supplied into the collision chamber is determined by the size of the incident ions when the gas molecules and gas pressure and the size of the collision chamber C are determined. It depends on the size and shape. However, there is no fixed definition of the size or shape of an atom or molecule, and the measurement method is a definition of size or shape, and it is said that the size or shape defined by a certain measurement method. Therefore, the above-mentioned size shape is also called a size shape in a certain sense. In any case, the probability of collision provides information on the size and shape of the ions incident on the collision chamber or the gas molecules supplied to the chamber, and the present invention detects this probability.

[Embodiment] An embodiment will be described with reference to the drawings.

In the example A, the ions that converge in the collision chamber C are known, and this is referred to as A ⁺ . A known gas B is introduced into the collision chamber C to maintain a constant pressure P. A ⁺ splits due to collision,
A ⁺ → A ′ ⁺ + A ″, and A ′ ⁺ is incident on the ion detector D (focused on the ion collector slit Ic).
The electric field E is set. The detection output of A ' ⁺ by D is Ib. Next, the gas introduced into the collision chamber C is changed to the unknown gas X, the pressure in the chamber is maintained at the same P as before, and A ′ ⁺
Ions are detected, and the output of the ion detector D at that time is I
Let x.

The frequency of collision between the ion A ⁺ in the collision chamber C and the gas molecule B or X is inversely proportional to the mean free path of the ion A ⁺ in the chamber. Let λb be the mean free path of A ⁺ when the gas of B is introduced into the collision chamber C and λx be the case of introducing the gas X, and let the atoms or molecules of the ions A ⁺ , the gases B and X be molecules. Let γa, γb, γx be the radii of Here, K is a constant that is determined by the gas pressure P in the collision chamber, and since P is constant in this case, K is also constant. The ion detector D detects the ion A ′ ⁺ , which is generated by collision of A ⁺ with gas molecules,
The output of the detector D is inversely proportional to the mean free path. Therefore, Ib = αK (γa + γb) ² and Ix = αK (γa + γx) ² where αK is unknown, but if the ratio of the above two equations is taken: In equation (1), Ib and Ix are actually measured values, and γa and γb are known, so γx can be obtained. This means that one piece of information has been obtained regarding the unknown gas X.

Embodiment B will be described using the same reference numerals as in the above example. In this embodiment, the ions A ⁺ are unknown and the gases B and X introduced into the collision chamber C are known. The mass number is known for A ⁺ . Γa is obtained from the equation (1). Even if the mass numbers are the same, the size and shape of A ⁺ are different depending on the elemental composition and the molecular structure. If the size and shape are different, γa will be different. Therefore, differences in samples that cannot be identified only by information such as mass number or molecular weight can be detected by this method.

F. Effect The method of the present invention is as described above, and provides novel analysis information that could not be obtained by the conventional instrumental analysis method, and the existing magnetic field preceding double-focusing mass spectrometer is used as the device. Therefore, the functions of this type of device can be expanded.

[Brief description of drawings]

The drawing is a plan view of a magnetic field precedent type double-focusing mass spectrometer. S ... Ion source, M ... Magnetic field, C ... Collision chamber, E ... Electric field, D ...
Ion detector.

Claims (1)

[Claims] 1. An apparatus in which an ion source, a mass spectrometric section, a collision chamber, an energy analysis section, and an ion detector are arranged in this order, and two kinds of gases are separately switched and supplied to the collision chamber at a constant pressure. Of the three of the ions that have converged in the collision chamber and the two types of gas that are supplied to the collision chamber, by obtaining the detection output of ions of specific energy when the two types of gas are supplied, respectively. A method for knowing the diameter of an atom or molecule, characterized by knowing the diameter of an atom or molecule for any one of the above.