“…Photoacoustic (PA) spectroscopy (PAS) has been one of the most versatile methods for trace gas analysis because of high sensitivity and selectivity [ 6 , 8 , [17] , [18] , [19] , [20] , [21] , [22] , [23] , [24] , [25] ]. In recent years, a lot of efforts have been made to optimize the PA systems by the researchers.…”