| 摘要 |
1,174,502. Mass spectrometers. VARIAN MAT G.m.b.H. 27 April, 1967 [25 June, 1966], No. 19390/67. Heading H1D. In a method of mass spectrometry in which the electron beam acceleration voltage of an electron beam bombardment type ion source is switched between two levels in order to distinguish between molecular masses very close together and in which the lower of the electron beam acceleration voltages lies in the steep commencement region of the ionization function of ion current i versus voltage V, Fig. 2, of at least one of the gaseous components, a gaseous component having particular properties is used as a standard to derive a control magnitude for maintaining the ion current constant in the steep commencement region of the ionization function of at least one of the gaseous components. The standardizing component has, in addition to clearly distinguishable and measurable mass peaks, an ionization function for which the lower electron beam acceleration voltage lies in the steep commencement region and the higher electron beam acceleration voltage lies in the maximum region where the ion current is substantially constant. The control magnitude corresponds to the ratio of the ion currents of the standardizing component derived with the two electron beam acceleration voltages U 1 + U 3 and U 2 + U 3 (U 2 > U 1 ) at the ion collector 11, Fig. 1. The ion current ratio is maintained constant in a preliminary compensation period by adjusting to equality at potentiometer 24 the derived voltages U 11 , U 12 , these voltages being applied via changeover relay 25 to a servo-amplifier 26 and servocontrol 27 for adjusting a variable voltage constituent U 3 of the electron beam acceleration voltage. The relays 25 and 16 are changed over in synchronism and the changeover period need not be divided into equal parts. After the compensation period under the control of a programme generator 17 the various ion currents at collectors 9, 10, 11 are recorded at each of the two electron beam acceleration voltage levels with provision being made for changeover of sensitivity at the potentiometers 28, 29, 30 which are in line with the recording devices 21, 22, 23. The standardizing component may be present in the gas mixture under analysis or added. Instead of utilizing simultaneous collection at a plurality of collectors 9, 10, 11 the mass spectrum may be scanned. |
