
Obtaining Good Spectra in Delayed Extraction Mode
Voyager
™
Biospectrometry
™
Workstation User’s Guide 6-23
6
6.3.2 Laser Intensity
Overview
Laser intensity does not have a major impact on resolution or
signal-to-noise ratio. You need to find the laser setting that
gives you an acceptable signal-to-noise ratio and acceptable
resolution (optimum is not necessary), and then fine-tune. If
adjusting Grid Voltage% and Delay Time causes the signal to
saturate, you may need to make additional laser adjustments.
For more information on adjusting the laser, see Section 5.4.2,
Determining the Laser Setting.
Continue acquiring and decreasing the laser intensity until you
observed a moderate resolution and a signal-to-noise ratio of
approximately 50:1.
Fragment ions
generated at
higher laser
intensity
Higher laser power can cause two types of fragment ions to
form:
• Prompt (fast) fragments—Form in the ion source before
ion acceleration, detected in Linear and Reflector mode.
• PSD (slow) fragments—Form in the flight tube after ion
acceleration, detected in Reflector mode.
Figure 6-10 shows a partial spectrum of Angiotensin I
obtained at high laser intensity in Reflector mode. The high
laser intensity has generated fragments.
Figure 6-10 Fragment Ions in Reflector Mode
Prompt
PSD
PSD
Prompt
Prompt
PSD
Mixture of
Prompt
and PSD
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