Zeeman modulation technique for Rapid Scanning FTR

Theory Theoretical analysis has made for z Zeeman modulated interferogram of rapid scanning FTR. It相信一个modulation frequency(fM) must be at least one or two magnitude higher than afrequencies of interferogram to eliminate modulation signals from interferogram by electronic lowpass filter. This leads a practical modulation frequency of ~ 20khz . For the Zeeman modulation，modulation frequency of 20khz is sometimes difficult to achieve，so some modification which avoids a limitation of fM . In this work low pass filter In a lock Inamplifier是removed and demodulated interferogram was accumulated in the memory of the computer.Accumulation of the interferogram was showed to eliminate a modulation signal. This方法允许我们to use a Zeeman modulation with 20hz for rapid scanning FTIR.Measurements Absorption cell equippeda solenoid coil which generated an ac magnetic field of 500g at 20hz . Absorption spectrum ofnitric oxide was measured at a resolution of 0.005 cm -1 - D1. nitric oxide has unpaired electron，leading a Zeeman effect The vibrational spectrum of nitric oxide was selectively measured from IRback ground which is not affected by external magnetic field。

Theory Theoretical analysis has made for z Zeeman modulated interferogram of rapid scanning FTR. It is believed that a modulation frequency(fM) must be at least one or two magnitude higher than a frequencies of interferogram(fF)to eliminate modulation signals from interferogram by electronic low pass filter. This leads a practical modulation frequency of 〜20 kHz. For the Zeeman modulation, the modulation frequency of 20 kHz is sometimes difficult to achieve, so some modification which avoids a limitation of fM ≫fF. In this work low pass filter in a lock in amplifier was removed and demodulated interferogram was accumulated in the memory of the computer. Accumulation of the interferogram was showed to eliminate a modulation signal. This method allow us to use a Zeeman modulation with 20 Hz for rapid scanning FTIR.Measurements Absorption cell equipped a solenoid coil which generated an ac magnetic field of 500 G at 20 Hz. Absorption spectrum of nitric oxide was measured at a resolution of 0.005 cmィイD1-1ィエD1. Nitric oxide has unpaired electron, leading a Zeeman effect. The vibrational spectrum of nitric oxide was selectively measured from IR back ground which is not affected by external magnetic field.